Merge github.com:grpc/grpc into cleaner-posix2

75 files changed, 11355 insertions, 0 deletions

diff --git a/src/core/lib/iomgr/closure.c b/src/core/lib/iomgr/closure.c
new file mode 100644
index 0000000000..724ebc284a
--- /dev/null
+++ b/src/core/lib/iomgr/closure.c
@@ -0,0 +1,98 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/closure.h"
+
+#include <grpc/support/alloc.h>
+
+void grpc_closure_init(grpc_closure *closure, grpc_iomgr_cb_func cb,
+                       void *cb_arg) {
+  closure->cb = cb;
+  closure->cb_arg = cb_arg;
+  closure->final_data = 0;
+}
+
+void grpc_closure_list_add(grpc_closure_list *closure_list,
+                           grpc_closure *closure, bool success) {
+  if (closure == NULL) return;
+  closure->final_data = (success != 0);
+  if (closure_list->head == NULL) {
+    closure_list->head = closure;
+  } else {
+    closure_list->tail->final_data |= (uintptr_t)closure;
+  }
+  closure_list->tail = closure;
+}
+
+bool grpc_closure_list_empty(grpc_closure_list closure_list) {
+  return closure_list.head == NULL;
+}
+
+void grpc_closure_list_move(grpc_closure_list *src, grpc_closure_list *dst) {
+  if (src->head == NULL) {
+    return;
+  }
+  if (dst->head == NULL) {
+    *dst = *src;
+  } else {
+    dst->tail->final_data |= (uintptr_t)src->head;
+    dst->tail = src->tail;
+  }
+  src->head = src->tail = NULL;
+}
+
+typedef struct {
+  grpc_iomgr_cb_func cb;
+  void *cb_arg;
+  grpc_closure wrapper;
+} wrapped_closure;
+
+static void closure_wrapper(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
+  wrapped_closure *wc = arg;
+  grpc_iomgr_cb_func cb = wc->cb;
+  void *cb_arg = wc->cb_arg;
+  gpr_free(wc);
+  cb(exec_ctx, cb_arg, success);
+}
+
+grpc_closure *grpc_closure_create(grpc_iomgr_cb_func cb, void *cb_arg) {
+  wrapped_closure *wc = gpr_malloc(sizeof(*wc));
+  wc->cb = cb;
+  wc->cb_arg = cb_arg;
+  grpc_closure_init(&wc->wrapper, closure_wrapper, wc);
+  return &wc->wrapper;
+}
+
+grpc_closure *grpc_closure_next(grpc_closure *closure) {
+  return (grpc_closure *)(closure->final_data & ~(uintptr_t)1);
+}
diff --git a/src/core/lib/iomgr/closure.h b/src/core/lib/iomgr/closure.h
new file mode 100644
index 0000000000..2597cf1706
--- /dev/null
+++ b/src/core/lib/iomgr/closure.h
@@ -0,0 +1,98 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_CLOSURE_H
+#define GRPC_CORE_LIB_IOMGR_CLOSURE_H
+
+#include <grpc/support/port_platform.h>
+#include <stdbool.h>
+
+struct grpc_closure;
+typedef struct grpc_closure grpc_closure;
+
+/* forward declaration for exec_ctx.h */
+struct grpc_exec_ctx;
+typedef struct grpc_exec_ctx grpc_exec_ctx;
+
+typedef struct grpc_closure_list {
+  grpc_closure *head;
+  grpc_closure *tail;
+} grpc_closure_list;
+
+/** gRPC Callback definition.
+ *
+ * \param arg Arbitrary input.
+ * \param success An indication on the state of the iomgr. On false, cleanup
+ * actions should be taken (eg, shutdown). */
+typedef void (*grpc_iomgr_cb_func)(grpc_exec_ctx *exec_ctx, void *arg,
+                                   bool success);
+
+/** A closure over a grpc_iomgr_cb_func. */
+struct grpc_closure {
+  /** Bound callback. */
+  grpc_iomgr_cb_func cb;
+
+  /** Arguments to be passed to "cb". */
+  void *cb_arg;
+
+  /** Once enqueued, contains in the lower bit the success of the closure,
+      and in the upper bits the pointer to the next closure in the list.
+      Before enqueing for execution, this is usable for scratch data. */
+  uintptr_t final_data;
+};
+
+/** Initializes \a closure with \a cb and \a cb_arg. */
+void grpc_closure_init(grpc_closure *closure, grpc_iomgr_cb_func cb,
+                       void *cb_arg);
+
+/* Create a heap allocated closure: try to avoid except for very rare events */
+grpc_closure *grpc_closure_create(grpc_iomgr_cb_func cb, void *cb_arg);
+
+#define GRPC_CLOSURE_LIST_INIT \
+  { NULL, NULL }
+
+/** add \a closure to the end of \a list and set \a closure's success to \a
+ * success */
+void grpc_closure_list_add(grpc_closure_list *list, grpc_closure *closure,
+                           bool success);
+
+/** append all closures from \a src to \a dst and empty \a src. */
+void grpc_closure_list_move(grpc_closure_list *src, grpc_closure_list *dst);
+
+/** return whether \a list is empty. */
+bool grpc_closure_list_empty(grpc_closure_list list);
+
+/** return the next pointer for a queued closure list */
+grpc_closure *grpc_closure_next(grpc_closure *closure);
+
+#endif /* GRPC_CORE_LIB_IOMGR_CLOSURE_H */
diff --git a/src/core/lib/iomgr/endpoint.c b/src/core/lib/iomgr/endpoint.c
new file mode 100644
index 0000000000..576b5a6e5c
--- /dev/null
+++ b/src/core/lib/iomgr/endpoint.c
@@ -0,0 +1,67 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/endpoint.h"
+
+void grpc_endpoint_read(grpc_exec_ctx* exec_ctx, grpc_endpoint* ep,
+                        gpr_slice_buffer* slices, grpc_closure* cb) {
+  ep->vtable->read(exec_ctx, ep, slices, cb);
+}
+
+void grpc_endpoint_write(grpc_exec_ctx* exec_ctx, grpc_endpoint* ep,
+                         gpr_slice_buffer* slices, grpc_closure* cb) {
+  ep->vtable->write(exec_ctx, ep, slices, cb);
+}
+
+void grpc_endpoint_add_to_pollset(grpc_exec_ctx* exec_ctx, grpc_endpoint* ep,
+                                  grpc_pollset* pollset) {
+  ep->vtable->add_to_pollset(exec_ctx, ep, pollset);
+}
+
+void grpc_endpoint_add_to_pollset_set(grpc_exec_ctx* exec_ctx,
+                                      grpc_endpoint* ep,
+                                      grpc_pollset_set* pollset_set) {
+  ep->vtable->add_to_pollset_set(exec_ctx, ep, pollset_set);
+}
+
+void grpc_endpoint_shutdown(grpc_exec_ctx* exec_ctx, grpc_endpoint* ep) {
+  ep->vtable->shutdown(exec_ctx, ep);
+}
+
+void grpc_endpoint_destroy(grpc_exec_ctx* exec_ctx, grpc_endpoint* ep) {
+  ep->vtable->destroy(exec_ctx, ep);
+}
+
+char* grpc_endpoint_get_peer(grpc_endpoint* ep) {
+  return ep->vtable->get_peer(ep);
+}
diff --git a/src/core/lib/iomgr/endpoint.h b/src/core/lib/iomgr/endpoint.h
new file mode 100644
index 0000000000..918e705fbd
--- /dev/null
+++ b/src/core/lib/iomgr/endpoint.h
@@ -0,0 +1,102 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_ENDPOINT_H
+#define GRPC_CORE_LIB_IOMGR_ENDPOINT_H
+
+#include <grpc/support/slice.h>
+#include <grpc/support/slice_buffer.h>
+#include <grpc/support/time.h>
+#include "src/core/lib/iomgr/pollset.h"
+#include "src/core/lib/iomgr/pollset_set.h"
+
+/* An endpoint caps a streaming channel between two communicating processes.
+   Examples may be: a tcp socket, <stdin+stdout>, or some shared memory. */
+
+typedef struct grpc_endpoint grpc_endpoint;
+typedef struct grpc_endpoint_vtable grpc_endpoint_vtable;
+
+struct grpc_endpoint_vtable {
+  void (*read)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+               gpr_slice_buffer *slices, grpc_closure *cb);
+  void (*write)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                gpr_slice_buffer *slices, grpc_closure *cb);
+  void (*add_to_pollset)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                         grpc_pollset *pollset);
+  void (*add_to_pollset_set)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                             grpc_pollset_set *pollset);
+  void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep);
+  void (*destroy)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep);
+  char *(*get_peer)(grpc_endpoint *ep);
+};
+
+/* When data is available on the connection, calls the callback with slices.
+   Callback success indicates that the endpoint can accept more reads, failure
+   indicates the endpoint is closed.
+   Valid slices may be placed into \a slices even on callback success == 0. */
+void grpc_endpoint_read(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                        gpr_slice_buffer *slices, grpc_closure *cb);
+
+char *grpc_endpoint_get_peer(grpc_endpoint *ep);
+
+/* Write slices out to the socket.
+
+   If the connection is ready for more data after the end of the call, it
+   returns GRPC_ENDPOINT_DONE.
+   Otherwise it returns GRPC_ENDPOINT_PENDING and calls cb when the
+   connection is ready for more data.
+   \a slices may be mutated at will by the endpoint until cb is called.
+   No guarantee is made to the content of slices after a write EXCEPT that
+   it is a valid slice buffer.
+   */
+void grpc_endpoint_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                         gpr_slice_buffer *slices, grpc_closure *cb);
+
+/* Causes any pending read/write callbacks to run immediately with
+   success==0 */
+void grpc_endpoint_shutdown(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep);
+void grpc_endpoint_destroy(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep);
+
+/* Add an endpoint to a pollset, so that when the pollset is polled, events from
+   this endpoint are considered */
+void grpc_endpoint_add_to_pollset(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                                  grpc_pollset *pollset);
+void grpc_endpoint_add_to_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_endpoint *ep,
+                                      grpc_pollset_set *pollset_set);
+
+struct grpc_endpoint {
+  const grpc_endpoint_vtable *vtable;
+};
+
+#endif /* GRPC_CORE_LIB_IOMGR_ENDPOINT_H */
diff --git a/src/core/lib/iomgr/endpoint_pair.h b/src/core/lib/iomgr/endpoint_pair.h
new file mode 100644
index 0000000000..bef8bb3518
--- /dev/null
+++ b/src/core/lib/iomgr/endpoint_pair.h
@@ -0,0 +1,47 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_ENDPOINT_PAIR_H
+#define GRPC_CORE_LIB_IOMGR_ENDPOINT_PAIR_H
+
+#include "src/core/lib/iomgr/endpoint.h"
+
+typedef struct {
+  grpc_endpoint *client;
+  grpc_endpoint *server;
+} grpc_endpoint_pair;
+
+grpc_endpoint_pair grpc_iomgr_create_endpoint_pair(const char *name,
+                                                   size_t read_slice_size);
+
+#endif /* GRPC_CORE_LIB_IOMGR_ENDPOINT_PAIR_H */
diff --git a/src/core/lib/iomgr/endpoint_pair_posix.c b/src/core/lib/iomgr/endpoint_pair_posix.c
new file mode 100644
index 0000000000..e0ce47c773
--- /dev/null
+++ b/src/core/lib/iomgr/endpoint_pair_posix.c
@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/endpoint_pair.h"
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include "src/core/lib/iomgr/tcp_posix.h"
+#include "src/core/lib/support/string.h"
+
+static void create_sockets(int sv[2]) {
+  int flags;
+  grpc_create_socketpair_if_unix(sv);
+  flags = fcntl(sv[0], F_GETFL, 0);
+  GPR_ASSERT(fcntl(sv[0], F_SETFL, flags | O_NONBLOCK) == 0);
+  flags = fcntl(sv[1], F_GETFL, 0);
+  GPR_ASSERT(fcntl(sv[1], F_SETFL, flags | O_NONBLOCK) == 0);
+  GPR_ASSERT(grpc_set_socket_no_sigpipe_if_possible(sv[0]));
+  GPR_ASSERT(grpc_set_socket_no_sigpipe_if_possible(sv[1]));
+}
+
+grpc_endpoint_pair grpc_iomgr_create_endpoint_pair(const char *name,
+                                                   size_t read_slice_size) {
+  int sv[2];
+  grpc_endpoint_pair p;
+  char *final_name;
+  create_sockets(sv);
+
+  gpr_asprintf(&final_name, "%s:client", name);
+  p.client = grpc_tcp_create(grpc_fd_create(sv[1], final_name), read_slice_size,
+                             "socketpair-server");
+  gpr_free(final_name);
+  gpr_asprintf(&final_name, "%s:server", name);
+  p.server = grpc_tcp_create(grpc_fd_create(sv[0], final_name), read_slice_size,
+                             "socketpair-client");
+  gpr_free(final_name);
+  return p;
+}
+
+#endif
diff --git a/src/core/lib/iomgr/endpoint_pair_windows.c b/src/core/lib/iomgr/endpoint_pair_windows.c
new file mode 100644
index 0000000000..cba18db81f
--- /dev/null
+++ b/src/core/lib/iomgr/endpoint_pair_windows.c
@@ -0,0 +1,97 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+#include "src/core/lib/iomgr/endpoint_pair.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+
+#include <grpc/support/log.h>
+#include "src/core/lib/iomgr/socket_windows.h"
+#include "src/core/lib/iomgr/tcp_windows.h"
+
+static void create_sockets(SOCKET sv[2]) {
+  SOCKET svr_sock = INVALID_SOCKET;
+  SOCKET lst_sock = INVALID_SOCKET;
+  SOCKET cli_sock = INVALID_SOCKET;
+  SOCKADDR_IN addr;
+  int addr_len = sizeof(addr);
+
+  lst_sock = WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0,
+                       WSA_FLAG_OVERLAPPED);
+  GPR_ASSERT(lst_sock != INVALID_SOCKET);
+
+  memset(&addr, 0, sizeof(addr));
+  addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  addr.sin_family = AF_INET;
+  GPR_ASSERT(bind(lst_sock, (struct sockaddr *)&addr, sizeof(addr)) !=
+             SOCKET_ERROR);
+  GPR_ASSERT(listen(lst_sock, SOMAXCONN) != SOCKET_ERROR);
+  GPR_ASSERT(getsockname(lst_sock, (struct sockaddr *)&addr, &addr_len) !=
+             SOCKET_ERROR);
+
+  cli_sock = WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0,
+                       WSA_FLAG_OVERLAPPED);
+  GPR_ASSERT(cli_sock != INVALID_SOCKET);
+
+  GPR_ASSERT(WSAConnect(cli_sock, (struct sockaddr *)&addr, addr_len, NULL,
+                        NULL, NULL, NULL) == 0);
+  svr_sock = accept(lst_sock, (struct sockaddr *)&addr, &addr_len);
+  GPR_ASSERT(svr_sock != INVALID_SOCKET);
+
+  closesocket(lst_sock);
+  grpc_tcp_prepare_socket(cli_sock);
+  grpc_tcp_prepare_socket(svr_sock);
+
+  sv[1] = cli_sock;
+  sv[0] = svr_sock;
+}
+
+grpc_endpoint_pair grpc_iomgr_create_endpoint_pair(const char *name,
+                                                   size_t read_slice_size) {
+  SOCKET sv[2];
+  grpc_endpoint_pair p;
+  create_sockets(sv);
+  p.client = grpc_tcp_create(grpc_winsocket_create(sv[1], "endpoint:client"),
+                             "endpoint:server");
+  p.server = grpc_tcp_create(grpc_winsocket_create(sv[0], "endpoint:server"),
+                             "endpoint:client");
+  return p;
+}
+
+#endif
diff --git a/src/core/lib/iomgr/ev_poll_and_epoll_posix.c b/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
new file mode 100644
index 0000000000..beccb9e89f
--- /dev/null
+++ b/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
@@ -0,0 +1,1934 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/* This file will be removed shortly: it's here to keep refactoring
+ * steps simple and auditable.
+ * It's the combination of the old files:
+ *  - fd_posix.{h,c}
+ *  - pollset_posix.{h,c}
+ *  - pullset_multipoller_with_{poll,epoll}.{h,c}
+ * The new version will be split into:
+ *  - ev_poll_posix.{h,c}
+ *  - ev_epoll_posix.{h,c}
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/ev_poll_and_epoll_posix.h"
+
+#include <assert.h>
+#include <errno.h>
+#include <poll.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/tls.h>
+#include <grpc/support/useful.h>
+
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+#include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/support/block_annotate.h"
+
+/*******************************************************************************
+ * FD declarations
+ */
+
+typedef struct grpc_fd_watcher {
+  struct grpc_fd_watcher *next;
+  struct grpc_fd_watcher *prev;
+  grpc_pollset *pollset;
+  grpc_pollset_worker *worker;
+  grpc_fd *fd;
+} grpc_fd_watcher;
+
+struct grpc_fd {
+  int fd;
+  /* refst format:
+     bit0:   1=active/0=orphaned
+     bit1-n: refcount
+     meaning that mostly we ref by two to avoid altering the orphaned bit,
+     and just unref by 1 when we're ready to flag the object as orphaned */
+  gpr_atm refst;
+
+  gpr_mu mu;
+  int shutdown;
+  int closed;
+  int released;
+
+  /* The watcher list.
+
+     The following watcher related fields are protected by watcher_mu.
+
+     An fd_watcher is an ephemeral object created when an fd wants to
+     begin polling, and destroyed after the poll.
+
+     It denotes the fd's interest in whether to read poll or write poll
+     or both or neither on this fd.
+
+     If a watcher is asked to poll for reads or writes, the read_watcher
+     or write_watcher fields are set respectively. A watcher may be asked
+     to poll for both, in which case both fields will be set.
+
+     read_watcher and write_watcher may be NULL if no watcher has been
+     asked to poll for reads or writes.
+
+     If an fd_watcher is not asked to poll for reads or writes, it's added
+     to a linked list of inactive watchers, rooted at inactive_watcher_root.
+     If at a later time there becomes need of a poller to poll, one of
+     the inactive pollers may be kicked out of their poll loops to take
+     that responsibility. */
+  grpc_fd_watcher inactive_watcher_root;
+  grpc_fd_watcher *read_watcher;
+  grpc_fd_watcher *write_watcher;
+
+  grpc_closure *read_closure;
+  grpc_closure *write_closure;
+
+  struct grpc_fd *freelist_next;
+
+  grpc_closure *on_done_closure;
+
+  grpc_iomgr_object iomgr_object;
+};
+
+/* Begin polling on an fd.
+   Registers that the given pollset is interested in this fd - so that if read
+   or writability interest changes, the pollset can be kicked to pick up that
+   new interest.
+   Return value is:
+     (fd_needs_read? read_mask : 0) | (fd_needs_write? write_mask : 0)
+   i.e. a combination of read_mask and write_mask determined by the fd's current
+   interest in said events.
+   Polling strategies that do not need to alter their behavior depending on the
+   fd's current interest (such as epoll) do not need to call this function.
+   MUST NOT be called with a pollset lock taken */
+static uint32_t fd_begin_poll(grpc_fd *fd, grpc_pollset *pollset,
+                              grpc_pollset_worker *worker, uint32_t read_mask,
+                              uint32_t write_mask, grpc_fd_watcher *rec);
+/* Complete polling previously started with fd_begin_poll
+   MUST NOT be called with a pollset lock taken
+   if got_read or got_write are 1, also does the become_{readable,writable} as
+   appropriate. */
+static void fd_end_poll(grpc_exec_ctx *exec_ctx, grpc_fd_watcher *rec,
+                        int got_read, int got_write);
+
+/* Return 1 if this fd is orphaned, 0 otherwise */
+static bool fd_is_orphaned(grpc_fd *fd);
+
+/* Reference counting for fds */
+/*#define GRPC_FD_REF_COUNT_DEBUG*/
+#ifdef GRPC_FD_REF_COUNT_DEBUG
+static void fd_ref(grpc_fd *fd, const char *reason, const char *file, int line);
+static void fd_unref(grpc_fd *fd, const char *reason, const char *file,
+                     int line);
+#define GRPC_FD_REF(fd, reason) fd_ref(fd, reason, __FILE__, __LINE__)
+#define GRPC_FD_UNREF(fd, reason) fd_unref(fd, reason, __FILE__, __LINE__)
+#else
+static void fd_ref(grpc_fd *fd);
+static void fd_unref(grpc_fd *fd);
+#define GRPC_FD_REF(fd, reason) fd_ref(fd)
+#define GRPC_FD_UNREF(fd, reason) fd_unref(fd)
+#endif
+
+static void fd_global_init(void);
+static void fd_global_shutdown(void);
+
+#define CLOSURE_NOT_READY ((grpc_closure *)0)
+#define CLOSURE_READY ((grpc_closure *)1)
+
+/*******************************************************************************
+ * pollset declarations
+ */
+
+typedef struct grpc_pollset_vtable grpc_pollset_vtable;
+
+typedef struct grpc_cached_wakeup_fd {
+  grpc_wakeup_fd fd;
+  struct grpc_cached_wakeup_fd *next;
+} grpc_cached_wakeup_fd;
+
+struct grpc_pollset_worker {
+  grpc_cached_wakeup_fd *wakeup_fd;
+  int reevaluate_polling_on_wakeup;
+  int kicked_specifically;
+  struct grpc_pollset_worker *next;
+  struct grpc_pollset_worker *prev;
+};
+
+struct grpc_pollset {
+  /* pollsets under posix can mutate representation as fds are added and
+     removed.
+     For example, we may choose a poll() based implementation on linux for
+     few fds, and an epoll() based implementation for many fds */
+  const grpc_pollset_vtable *vtable;
+  gpr_mu mu;
+  grpc_pollset_worker root_worker;
+  int in_flight_cbs;
+  int shutting_down;
+  int called_shutdown;
+  int kicked_without_pollers;
+  grpc_closure *shutdown_done;
+  grpc_closure_list idle_jobs;
+  union {
+    int fd;
+    void *ptr;
+  } data;
+  /* Local cache of eventfds for workers */
+  grpc_cached_wakeup_fd *local_wakeup_cache;
+};
+
+struct grpc_pollset_vtable {
+  void (*add_fd)(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                 struct grpc_fd *fd, int and_unlock_pollset);
+  void (*maybe_work_and_unlock)(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                                grpc_pollset_worker *worker,
+                                gpr_timespec deadline, gpr_timespec now);
+  void (*finish_shutdown)(grpc_pollset *pollset);
+  void (*destroy)(grpc_pollset *pollset);
+};
+
+/* Add an fd to a pollset */
+static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           struct grpc_fd *fd);
+
+static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
+                               grpc_pollset_set *pollset_set, grpc_fd *fd);
+
+/* Convert a timespec to milliseconds:
+   - very small or negative poll times are clamped to zero to do a
+     non-blocking poll (which becomes spin polling)
+   - other small values are rounded up to one millisecond
+   - longer than a millisecond polls are rounded up to the next nearest
+     millisecond to avoid spinning
+   - infinite timeouts are converted to -1 */
+static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
+                                           gpr_timespec now);
+
+/* Allow kick to wakeup the currently polling worker */
+#define GRPC_POLLSET_CAN_KICK_SELF 1
+/* Force the wakee to repoll when awoken */
+#define GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP 2
+/* As per pollset_kick, with an extended set of flags (defined above)
+   -- mostly for fd_posix's use. */
+static void pollset_kick_ext(grpc_pollset *p,
+                             grpc_pollset_worker *specific_worker,
+                             uint32_t flags);
+
+/* turn a pollset into a multipoller: platform specific */
+typedef void (*platform_become_multipoller_type)(grpc_exec_ctx *exec_ctx,
+                                                 grpc_pollset *pollset,
+                                                 struct grpc_fd **fds,
+                                                 size_t fd_count);
+static platform_become_multipoller_type platform_become_multipoller;
+
+/* Return 1 if the pollset has active threads in pollset_work (pollset must
+ * be locked) */
+static int pollset_has_workers(grpc_pollset *pollset);
+
+static void remove_fd_from_all_epoll_sets(int fd);
+
+/*******************************************************************************
+ * pollset_set definitions
+ */
+
+struct grpc_pollset_set {
+  gpr_mu mu;
+
+  size_t pollset_count;
+  size_t pollset_capacity;
+  grpc_pollset **pollsets;
+
+  size_t pollset_set_count;
+  size_t pollset_set_capacity;
+  struct grpc_pollset_set **pollset_sets;
+
+  size_t fd_count;
+  size_t fd_capacity;
+  grpc_fd **fds;
+};
+
+/*******************************************************************************
+ * fd_posix.c
+ */
+
+/* We need to keep a freelist not because of any concerns of malloc performance
+ * but instead so that implementations with multiple threads in (for example)
+ * epoll_wait deal with the race between pollset removal and incoming poll
+ * notifications.
+ *
+ * The problem is that the poller ultimately holds a reference to this
+ * object, so it is very difficult to know when is safe to free it, at least
+ * without some expensive synchronization.
+ *
+ * If we keep the object freelisted, in the worst case losing this race just
+ * becomes a spurious read notification on a reused fd.
+ */
+/* TODO(klempner): We could use some form of polling generation count to know
+ * when these are safe to free. */
+/* TODO(klempner): Consider disabling freelisting if we don't have multiple
+ * threads in poll on the same fd */
+/* TODO(klempner): Batch these allocations to reduce fragmentation */
+static grpc_fd *fd_freelist = NULL;
+static gpr_mu fd_freelist_mu;
+
+static void freelist_fd(grpc_fd *fd) {
+  gpr_mu_lock(&fd_freelist_mu);
+  fd->freelist_next = fd_freelist;
+  fd_freelist = fd;
+  grpc_iomgr_unregister_object(&fd->iomgr_object);
+  gpr_mu_unlock(&fd_freelist_mu);
+}
+
+static grpc_fd *alloc_fd(int fd) {
+  grpc_fd *r = NULL;
+  gpr_mu_lock(&fd_freelist_mu);
+  if (fd_freelist != NULL) {
+    r = fd_freelist;
+    fd_freelist = fd_freelist->freelist_next;
+  }
+  gpr_mu_unlock(&fd_freelist_mu);
+  if (r == NULL) {
+    r = gpr_malloc(sizeof(grpc_fd));
+    gpr_mu_init(&r->mu);
+  }
+
+  gpr_atm_rel_store(&r->refst, 1);
+  r->shutdown = 0;
+  r->read_closure = CLOSURE_NOT_READY;
+  r->write_closure = CLOSURE_NOT_READY;
+  r->fd = fd;
+  r->inactive_watcher_root.next = r->inactive_watcher_root.prev =
+      &r->inactive_watcher_root;
+  r->freelist_next = NULL;
+  r->read_watcher = r->write_watcher = NULL;
+  r->on_done_closure = NULL;
+  r->closed = 0;
+  r->released = 0;
+  return r;
+}
+
+static void destroy(grpc_fd *fd) {
+  gpr_mu_destroy(&fd->mu);
+  gpr_free(fd);
+}
+
+#ifdef GRPC_FD_REF_COUNT_DEBUG
+#define REF_BY(fd, n, reason) ref_by(fd, n, reason, __FILE__, __LINE__)
+#define UNREF_BY(fd, n, reason) unref_by(fd, n, reason, __FILE__, __LINE__)
+static void ref_by(grpc_fd *fd, int n, const char *reason, const char *file,
+                   int line) {
+  gpr_log(GPR_DEBUG, "FD %d %p   ref %d %d -> %d [%s; %s:%d]", fd->fd, fd, n,
+          gpr_atm_no_barrier_load(&fd->refst),
+          gpr_atm_no_barrier_load(&fd->refst) + n, reason, file, line);
+#else
+#define REF_BY(fd, n, reason) ref_by(fd, n)
+#define UNREF_BY(fd, n, reason) unref_by(fd, n)
+static void ref_by(grpc_fd *fd, int n) {
+#endif
+  GPR_ASSERT(gpr_atm_no_barrier_fetch_add(&fd->refst, n) > 0);
+}
+
+#ifdef GRPC_FD_REF_COUNT_DEBUG
+static void unref_by(grpc_fd *fd, int n, const char *reason, const char *file,
+                     int line) {
+  gpr_atm old;
+  gpr_log(GPR_DEBUG, "FD %d %p unref %d %d -> %d [%s; %s:%d]", fd->fd, fd, n,
+          gpr_atm_no_barrier_load(&fd->refst),
+          gpr_atm_no_barrier_load(&fd->refst) - n, reason, file, line);
+#else
+static void unref_by(grpc_fd *fd, int n) {
+  gpr_atm old;
+#endif
+  old = gpr_atm_full_fetch_add(&fd->refst, -n);
+  if (old == n) {
+    freelist_fd(fd);
+  } else {
+    GPR_ASSERT(old > n);
+  }
+}
+
+static void fd_global_init(void) { gpr_mu_init(&fd_freelist_mu); }
+
+static void fd_global_shutdown(void) {
+  gpr_mu_lock(&fd_freelist_mu);
+  gpr_mu_unlock(&fd_freelist_mu);
+  while (fd_freelist != NULL) {
+    grpc_fd *fd = fd_freelist;
+    fd_freelist = fd_freelist->freelist_next;
+    destroy(fd);
+  }
+  gpr_mu_destroy(&fd_freelist_mu);
+}
+
+static grpc_fd *fd_create(int fd, const char *name) {
+  grpc_fd *r = alloc_fd(fd);
+  char *name2;
+  gpr_asprintf(&name2, "%s fd=%d", name, fd);
+  grpc_iomgr_register_object(&r->iomgr_object, name2);
+  gpr_free(name2);
+#ifdef GRPC_FD_REF_COUNT_DEBUG
+  gpr_log(GPR_DEBUG, "FD %d %p create %s", fd, r, name);
+#endif
+  return r;
+}
+
+static bool fd_is_orphaned(grpc_fd *fd) {
+  return (gpr_atm_acq_load(&fd->refst) & 1) == 0;
+}
+
+static void pollset_kick_locked(grpc_fd_watcher *watcher) {
+  gpr_mu_lock(&watcher->pollset->mu);
+  GPR_ASSERT(watcher->worker);
+  pollset_kick_ext(watcher->pollset, watcher->worker,
+                   GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP);
+  gpr_mu_unlock(&watcher->pollset->mu);
+}
+
+static void maybe_wake_one_watcher_locked(grpc_fd *fd) {
+  if (fd->inactive_watcher_root.next != &fd->inactive_watcher_root) {
+    pollset_kick_locked(fd->inactive_watcher_root.next);
+  } else if (fd->read_watcher) {
+    pollset_kick_locked(fd->read_watcher);
+  } else if (fd->write_watcher) {
+    pollset_kick_locked(fd->write_watcher);
+  }
+}
+
+static void wake_all_watchers_locked(grpc_fd *fd) {
+  grpc_fd_watcher *watcher;
+  for (watcher = fd->inactive_watcher_root.next;
+       watcher != &fd->inactive_watcher_root; watcher = watcher->next) {
+    pollset_kick_locked(watcher);
+  }
+  if (fd->read_watcher) {
+    pollset_kick_locked(fd->read_watcher);
+  }
+  if (fd->write_watcher && fd->write_watcher != fd->read_watcher) {
+    pollset_kick_locked(fd->write_watcher);
+  }
+}
+
+static int has_watchers(grpc_fd *fd) {
+  return fd->read_watcher != NULL || fd->write_watcher != NULL ||
+         fd->inactive_watcher_root.next != &fd->inactive_watcher_root;
+}
+
+static void close_fd_locked(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
+  fd->closed = 1;
+  if (!fd->released) {
+    close(fd->fd);
+  } else {
+    remove_fd_from_all_epoll_sets(fd->fd);
+  }
+  grpc_exec_ctx_enqueue(exec_ctx, fd->on_done_closure, true, NULL);
+}
+
+static int fd_wrapped_fd(grpc_fd *fd) {
+  if (fd->released || fd->closed) {
+    return -1;
+  } else {
+    return fd->fd;
+  }
+}
+
+static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                      grpc_closure *on_done, int *release_fd,
+                      const char *reason) {
+  fd->on_done_closure = on_done;
+  fd->released = release_fd != NULL;
+  if (!fd->released) {
+    shutdown(fd->fd, SHUT_RDWR);
+  } else {
+    *release_fd = fd->fd;
+  }
+  gpr_mu_lock(&fd->mu);
+  REF_BY(fd, 1, reason); /* remove active status, but keep referenced */
+  if (!has_watchers(fd)) {
+    close_fd_locked(exec_ctx, fd);
+  } else {
+    wake_all_watchers_locked(fd);
+  }
+  gpr_mu_unlock(&fd->mu);
+  UNREF_BY(fd, 2, reason); /* drop the reference */
+}
+
+/* increment refcount by two to avoid changing the orphan bit */
+#ifdef GRPC_FD_REF_COUNT_DEBUG
+static void fd_ref(grpc_fd *fd, const char *reason, const char *file,
+                   int line) {
+  ref_by(fd, 2, reason, file, line);
+}
+
+static void fd_unref(grpc_fd *fd, const char *reason, const char *file,
+                     int line) {
+  unref_by(fd, 2, reason, file, line);
+}
+#else
+static void fd_ref(grpc_fd *fd) { ref_by(fd, 2); }
+
+static void fd_unref(grpc_fd *fd) { unref_by(fd, 2); }
+#endif
+
+static void notify_on_locked(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                             grpc_closure **st, grpc_closure *closure) {
+  if (*st == CLOSURE_NOT_READY) {
+    /* not ready ==> switch to a waiting state by setting the closure */
+    *st = closure;
+  } else if (*st == CLOSURE_READY) {
+    /* already ready ==> queue the closure to run immediately */
+    *st = CLOSURE_NOT_READY;
+    grpc_exec_ctx_enqueue(exec_ctx, closure, !fd->shutdown, NULL);
+    maybe_wake_one_watcher_locked(fd);
+  } else {
+    /* upcallptr was set to a different closure.  This is an error! */
+    gpr_log(GPR_ERROR,
+            "User called a notify_on function with a previous callback still "
+            "pending");
+    abort();
+  }
+}
+
+/* returns 1 if state becomes not ready */
+static int set_ready_locked(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                            grpc_closure **st) {
+  if (*st == CLOSURE_READY) {
+    /* duplicate ready ==> ignore */
+    return 0;
+  } else if (*st == CLOSURE_NOT_READY) {
+    /* not ready, and not waiting ==> flag ready */
+    *st = CLOSURE_READY;
+    return 0;
+  } else {
+    /* waiting ==> queue closure */
+    grpc_exec_ctx_enqueue(exec_ctx, *st, !fd->shutdown, NULL);
+    *st = CLOSURE_NOT_READY;
+    return 1;
+  }
+}
+
+static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
+  gpr_mu_lock(&fd->mu);
+  GPR_ASSERT(!fd->shutdown);
+  fd->shutdown = 1;
+  set_ready_locked(exec_ctx, fd, &fd->read_closure);
+  set_ready_locked(exec_ctx, fd, &fd->write_closure);
+  gpr_mu_unlock(&fd->mu);
+}
+
+static void fd_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                              grpc_closure *closure) {
+  gpr_mu_lock(&fd->mu);
+  notify_on_locked(exec_ctx, fd, &fd->read_closure, closure);
+  gpr_mu_unlock(&fd->mu);
+}
+
+static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                               grpc_closure *closure) {
+  gpr_mu_lock(&fd->mu);
+  notify_on_locked(exec_ctx, fd, &fd->write_closure, closure);
+  gpr_mu_unlock(&fd->mu);
+}
+
+static uint32_t fd_begin_poll(grpc_fd *fd, grpc_pollset *pollset,
+                              grpc_pollset_worker *worker, uint32_t read_mask,
+                              uint32_t write_mask, grpc_fd_watcher *watcher) {
+  uint32_t mask = 0;
+  grpc_closure *cur;
+  int requested;
+  /* keep track of pollers that have requested our events, in case they change
+   */
+  GRPC_FD_REF(fd, "poll");
+
+  gpr_mu_lock(&fd->mu);
+
+  /* if we are shutdown, then don't add to the watcher set */
+  if (fd->shutdown) {
+    watcher->fd = NULL;
+    watcher->pollset = NULL;
+    watcher->worker = NULL;
+    gpr_mu_unlock(&fd->mu);
+    GRPC_FD_UNREF(fd, "poll");
+    return 0;
+  }
+
+  /* if there is nobody polling for read, but we need to, then start doing so */
+  cur = fd->read_closure;
+  requested = cur != CLOSURE_READY;
+  if (read_mask && fd->read_watcher == NULL && requested) {
+    fd->read_watcher = watcher;
+    mask |= read_mask;
+  }
+  /* if there is nobody polling for write, but we need to, then start doing so
+   */
+  cur = fd->write_closure;
+  requested = cur != CLOSURE_READY;
+  if (write_mask && fd->write_watcher == NULL && requested) {
+    fd->write_watcher = watcher;
+    mask |= write_mask;
+  }
+  /* if not polling, remember this watcher in case we need someone to later */
+  if (mask == 0 && worker != NULL) {
+    watcher->next = &fd->inactive_watcher_root;
+    watcher->prev = watcher->next->prev;
+    watcher->next->prev = watcher->prev->next = watcher;
+  }
+  watcher->pollset = pollset;
+  watcher->worker = worker;
+  watcher->fd = fd;
+  gpr_mu_unlock(&fd->mu);
+
+  return mask;
+}
+
+static void fd_end_poll(grpc_exec_ctx *exec_ctx, grpc_fd_watcher *watcher,
+                        int got_read, int got_write) {
+  int was_polling = 0;
+  int kick = 0;
+  grpc_fd *fd = watcher->fd;
+
+  if (fd == NULL) {
+    return;
+  }
+
+  gpr_mu_lock(&fd->mu);
+
+  if (watcher == fd->read_watcher) {
+    /* remove read watcher, kick if we still need a read */
+    was_polling = 1;
+    if (!got_read) {
+      kick = 1;
+    }
+    fd->read_watcher = NULL;
+  }
+  if (watcher == fd->write_watcher) {
+    /* remove write watcher, kick if we still need a write */
+    was_polling = 1;
+    if (!got_write) {
+      kick = 1;
+    }
+    fd->write_watcher = NULL;
+  }
+  if (!was_polling && watcher->worker != NULL) {
+    /* remove from inactive list */
+    watcher->next->prev = watcher->prev;
+    watcher->prev->next = watcher->next;
+  }
+  if (got_read) {
+    if (set_ready_locked(exec_ctx, fd, &fd->read_closure)) {
+      kick = 1;
+    }
+  }
+  if (got_write) {
+    if (set_ready_locked(exec_ctx, fd, &fd->write_closure)) {
+      kick = 1;
+    }
+  }
+  if (kick) {
+    maybe_wake_one_watcher_locked(fd);
+  }
+  if (fd_is_orphaned(fd) && !has_watchers(fd) && !fd->closed) {
+    close_fd_locked(exec_ctx, fd);
+  }
+  gpr_mu_unlock(&fd->mu);
+
+  GRPC_FD_UNREF(fd, "poll");
+}
+
+/*******************************************************************************
+ * pollset_posix.c
+ */
+
+GPR_TLS_DECL(g_current_thread_poller);
+GPR_TLS_DECL(g_current_thread_worker);
+
+/** The alarm system needs to be able to wakeup 'some poller' sometimes
+ *  (specifically when a new alarm needs to be triggered earlier than the next
+ *  alarm 'epoch').
+ *  This wakeup_fd gives us something to alert on when such a case occurs. */
+grpc_wakeup_fd grpc_global_wakeup_fd;
+
+static void remove_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
+  worker->prev->next = worker->next;
+  worker->next->prev = worker->prev;
+}
+
+static int pollset_has_workers(grpc_pollset *p) {
+  return p->root_worker.next != &p->root_worker;
+}
+
+static grpc_pollset_worker *pop_front_worker(grpc_pollset *p) {
+  if (pollset_has_workers(p)) {
+    grpc_pollset_worker *w = p->root_worker.next;
+    remove_worker(p, w);
+    return w;
+  } else {
+    return NULL;
+  }
+}
+
+static void push_back_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
+  worker->next = &p->root_worker;
+  worker->prev = worker->next->prev;
+  worker->prev->next = worker->next->prev = worker;
+}
+
+static void push_front_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
+  worker->prev = &p->root_worker;
+  worker->next = worker->prev->next;
+  worker->prev->next = worker->next->prev = worker;
+}
+
+static void pollset_kick_ext(grpc_pollset *p,
+                             grpc_pollset_worker *specific_worker,
+                             uint32_t flags) {
+  GPR_TIMER_BEGIN("pollset_kick_ext", 0);
+
+  /* pollset->mu already held */
+  if (specific_worker != NULL) {
+    if (specific_worker == GRPC_POLLSET_KICK_BROADCAST) {
+      GPR_TIMER_BEGIN("pollset_kick_ext.broadcast", 0);
+      GPR_ASSERT((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) == 0);
+      for (specific_worker = p->root_worker.next;
+           specific_worker != &p->root_worker;
+           specific_worker = specific_worker->next) {
+        grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd);
+      }
+      p->kicked_without_pollers = 1;
+      GPR_TIMER_END("pollset_kick_ext.broadcast", 0);
+    } else if (gpr_tls_get(&g_current_thread_worker) !=
+               (intptr_t)specific_worker) {
+      GPR_TIMER_MARK("different_thread_worker", 0);
+      if ((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) != 0) {
+        specific_worker->reevaluate_polling_on_wakeup = 1;
+      }
+      specific_worker->kicked_specifically = 1;
+      grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd);
+    } else if ((flags & GRPC_POLLSET_CAN_KICK_SELF) != 0) {
+      GPR_TIMER_MARK("kick_yoself", 0);
+      if ((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) != 0) {
+        specific_worker->reevaluate_polling_on_wakeup = 1;
+      }
+      specific_worker->kicked_specifically = 1;
+      grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd);
+    }
+  } else if (gpr_tls_get(&g_current_thread_poller) != (intptr_t)p) {
+    GPR_ASSERT((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) == 0);
+    GPR_TIMER_MARK("kick_anonymous", 0);
+    specific_worker = pop_front_worker(p);
+    if (specific_worker != NULL) {
+      if (gpr_tls_get(&g_current_thread_worker) == (intptr_t)specific_worker) {
+        GPR_TIMER_MARK("kick_anonymous_not_self", 0);
+        push_back_worker(p, specific_worker);
+        specific_worker = pop_front_worker(p);
+        if ((flags & GRPC_POLLSET_CAN_KICK_SELF) == 0 &&
+            gpr_tls_get(&g_current_thread_worker) ==
+                (intptr_t)specific_worker) {
+          push_back_worker(p, specific_worker);
+          specific_worker = NULL;
+        }
+      }
+      if (specific_worker != NULL) {
+        GPR_TIMER_MARK("finally_kick", 0);
+        push_back_worker(p, specific_worker);
+        grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd);
+      }
+    } else {
+      GPR_TIMER_MARK("kicked_no_pollers", 0);
+      p->kicked_without_pollers = 1;
+    }
+  }
+
+  GPR_TIMER_END("pollset_kick_ext", 0);
+}
+
+static void pollset_kick(grpc_pollset *p,
+                         grpc_pollset_worker *specific_worker) {
+  pollset_kick_ext(p, specific_worker, 0);
+}
+
+/* global state management */
+
+static void pollset_global_init(void) {
+  gpr_tls_init(&g_current_thread_poller);
+  gpr_tls_init(&g_current_thread_worker);
+  grpc_wakeup_fd_global_init();
+  grpc_wakeup_fd_init(&grpc_global_wakeup_fd);
+}
+
+static void pollset_global_shutdown(void) {
+  grpc_wakeup_fd_destroy(&grpc_global_wakeup_fd);
+  gpr_tls_destroy(&g_current_thread_poller);
+  gpr_tls_destroy(&g_current_thread_worker);
+  grpc_wakeup_fd_global_destroy();
+}
+
+static void kick_poller(void) { grpc_wakeup_fd_wakeup(&grpc_global_wakeup_fd); }
+
+/* main interface */
+
+static void become_basic_pollset(grpc_pollset *pollset, grpc_fd *fd_or_null);
+
+static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
+  gpr_mu_init(&pollset->mu);
+  *mu = &pollset->mu;
+  pollset->root_worker.next = pollset->root_worker.prev = &pollset->root_worker;
+  pollset->in_flight_cbs = 0;
+  pollset->shutting_down = 0;
+  pollset->called_shutdown = 0;
+  pollset->kicked_without_pollers = 0;
+  pollset->idle_jobs.head = pollset->idle_jobs.tail = NULL;
+  pollset->local_wakeup_cache = NULL;
+  pollset->kicked_without_pollers = 0;
+  become_basic_pollset(pollset, NULL);
+}
+
+static void pollset_destroy(grpc_pollset *pollset) {
+  GPR_ASSERT(pollset->in_flight_cbs == 0);
+  GPR_ASSERT(!pollset_has_workers(pollset));
+  GPR_ASSERT(pollset->idle_jobs.head == pollset->idle_jobs.tail);
+  pollset->vtable->destroy(pollset);
+  while (pollset->local_wakeup_cache) {
+    grpc_cached_wakeup_fd *next = pollset->local_wakeup_cache->next;
+    grpc_wakeup_fd_destroy(&pollset->local_wakeup_cache->fd);
+    gpr_free(pollset->local_wakeup_cache);
+    pollset->local_wakeup_cache = next;
+  }
+  gpr_mu_destroy(&pollset->mu);
+}
+
+static void pollset_reset(grpc_pollset *pollset) {
+  GPR_ASSERT(pollset->shutting_down);
+  GPR_ASSERT(pollset->in_flight_cbs == 0);
+  GPR_ASSERT(!pollset_has_workers(pollset));
+  GPR_ASSERT(pollset->idle_jobs.head == pollset->idle_jobs.tail);
+  pollset->vtable->destroy(pollset);
+  pollset->shutting_down = 0;
+  pollset->called_shutdown = 0;
+  pollset->kicked_without_pollers = 0;
+  become_basic_pollset(pollset, NULL);
+}
+
+static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           grpc_fd *fd) {
+  gpr_mu_lock(&pollset->mu);
+  pollset->vtable->add_fd(exec_ctx, pollset, fd, 1);
+/* the following (enabled only in debug) will reacquire and then release
+   our lock - meaning that if the unlocking flag passed to add_fd above is
+   not respected, the code will deadlock (in a way that we have a chance of
+   debugging) */
+#ifndef NDEBUG
+  gpr_mu_lock(&pollset->mu);
+  gpr_mu_unlock(&pollset->mu);
+#endif
+}
+
+static void finish_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
+  GPR_ASSERT(grpc_closure_list_empty(pollset->idle_jobs));
+  pollset->vtable->finish_shutdown(pollset);
+  grpc_exec_ctx_enqueue(exec_ctx, pollset->shutdown_done, true, NULL);
+}
+
+static void pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                         grpc_pollset_worker **worker_hdl, gpr_timespec now,
+                         gpr_timespec deadline) {
+  grpc_pollset_worker worker;
+  *worker_hdl = &worker;
+
+  /* pollset->mu already held */
+  int added_worker = 0;
+  int locked = 1;
+  int queued_work = 0;
+  int keep_polling = 0;
+  GPR_TIMER_BEGIN("pollset_work", 0);
+  /* this must happen before we (potentially) drop pollset->mu */
+  worker.next = worker.prev = NULL;
+  worker.reevaluate_polling_on_wakeup = 0;
+  if (pollset->local_wakeup_cache != NULL) {
+    worker.wakeup_fd = pollset->local_wakeup_cache;
+    pollset->local_wakeup_cache = worker.wakeup_fd->next;
+  } else {
+    worker.wakeup_fd = gpr_malloc(sizeof(*worker.wakeup_fd));
+    grpc_wakeup_fd_init(&worker.wakeup_fd->fd);
+  }
+  worker.kicked_specifically = 0;
+  /* If there's work waiting for the pollset to be idle, and the
+     pollset is idle, then do that work */
+  if (!pollset_has_workers(pollset) &&
+      !grpc_closure_list_empty(pollset->idle_jobs)) {
+    GPR_TIMER_MARK("pollset_work.idle_jobs", 0);
+    grpc_exec_ctx_enqueue_list(exec_ctx, &pollset->idle_jobs, NULL);
+    goto done;
+  }
+  /* If we're shutting down then we don't execute any extended work */
+  if (pollset->shutting_down) {
+    GPR_TIMER_MARK("pollset_work.shutting_down", 0);
+    goto done;
+  }
+  /* Give do_promote priority so we don't starve it out */
+  if (pollset->in_flight_cbs) {
+    GPR_TIMER_MARK("pollset_work.in_flight_cbs", 0);
+    gpr_mu_unlock(&pollset->mu);
+    locked = 0;
+    goto done;
+  }
+  /* Start polling, and keep doing so while we're being asked to
+     re-evaluate our pollers (this allows poll() based pollers to
+     ensure they don't miss wakeups) */
+  keep_polling = 1;
+  while (keep_polling) {
+    keep_polling = 0;
+    if (!pollset->kicked_without_pollers) {
+      if (!added_worker) {
+        push_front_worker(pollset, &worker);
+        added_worker = 1;
+        gpr_tls_set(&g_current_thread_worker, (intptr_t)&worker);
+      }
+      gpr_tls_set(&g_current_thread_poller, (intptr_t)pollset);
+      GPR_TIMER_BEGIN("maybe_work_and_unlock", 0);
+      pollset->vtable->maybe_work_and_unlock(exec_ctx, pollset, &worker,
+                                             deadline, now);
+      GPR_TIMER_END("maybe_work_and_unlock", 0);
+      locked = 0;
+      gpr_tls_set(&g_current_thread_poller, 0);
+    } else {
+      GPR_TIMER_MARK("pollset_work.kicked_without_pollers", 0);
+      pollset->kicked_without_pollers = 0;
+    }
+  /* Finished execution - start cleaning up.
+     Note that we may arrive here from outside the enclosing while() loop.
+     In that case we won't loop though as we haven't added worker to the
+     worker list, which means nobody could ask us to re-evaluate polling). */
+  done:
+    if (!locked) {
+      queued_work |= grpc_exec_ctx_flush(exec_ctx);
+      gpr_mu_lock(&pollset->mu);
+      locked = 1;
+    }
+    /* If we're forced to re-evaluate polling (via pollset_kick with
+       GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) then we land here and force
+       a loop */
+    if (worker.reevaluate_polling_on_wakeup) {
+      worker.reevaluate_polling_on_wakeup = 0;
+      pollset->kicked_without_pollers = 0;
+      if (queued_work || worker.kicked_specifically) {
+        /* If there's queued work on the list, then set the deadline to be
+           immediate so we get back out of the polling loop quickly */
+        deadline = gpr_inf_past(GPR_CLOCK_MONOTONIC);
+      }
+      keep_polling = 1;
+    }
+  }
+  if (added_worker) {
+    remove_worker(pollset, &worker);
+    gpr_tls_set(&g_current_thread_worker, 0);
+  }
+  /* release wakeup fd to the local pool */
+  worker.wakeup_fd->next = pollset->local_wakeup_cache;
+  pollset->local_wakeup_cache = worker.wakeup_fd;
+  /* check shutdown conditions */
+  if (pollset->shutting_down) {
+    if (pollset_has_workers(pollset)) {
+      pollset_kick(pollset, NULL);
+    } else if (!pollset->called_shutdown && pollset->in_flight_cbs == 0) {
+      pollset->called_shutdown = 1;
+      gpr_mu_unlock(&pollset->mu);
+      finish_shutdown(exec_ctx, pollset);
+      grpc_exec_ctx_flush(exec_ctx);
+      /* Continuing to access pollset here is safe -- it is the caller's
+       * responsibility to not destroy when it has outstanding calls to
+       * pollset_work.
+       * TODO(dklempner): Can we refactor the shutdown logic to avoid this? */
+      gpr_mu_lock(&pollset->mu);
+    } else if (!grpc_closure_list_empty(pollset->idle_jobs)) {
+      grpc_exec_ctx_enqueue_list(exec_ctx, &pollset->idle_jobs, NULL);
+      gpr_mu_unlock(&pollset->mu);
+      grpc_exec_ctx_flush(exec_ctx);
+      gpr_mu_lock(&pollset->mu);
+    }
+  }
+  *worker_hdl = NULL;
+  GPR_TIMER_END("pollset_work", 0);
+}
+
+static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                             grpc_closure *closure) {
+  GPR_ASSERT(!pollset->shutting_down);
+  pollset->shutting_down = 1;
+  pollset->shutdown_done = closure;
+  pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
+  if (!pollset_has_workers(pollset)) {
+    grpc_exec_ctx_enqueue_list(exec_ctx, &pollset->idle_jobs, NULL);
+  }
+  if (!pollset->called_shutdown && pollset->in_flight_cbs == 0 &&
+      !pollset_has_workers(pollset)) {
+    pollset->called_shutdown = 1;
+    finish_shutdown(exec_ctx, pollset);
+  }
+}
+
+static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
+                                           gpr_timespec now) {
+  gpr_timespec timeout;
+  static const int64_t max_spin_polling_us = 10;
+  if (gpr_time_cmp(deadline, gpr_inf_future(deadline.clock_type)) == 0) {
+    return -1;
+  }
+  if (gpr_time_cmp(deadline, gpr_time_add(now, gpr_time_from_micros(
+                                                   max_spin_polling_us,
+                                                   GPR_TIMESPAN))) <= 0) {
+    return 0;
+  }
+  timeout = gpr_time_sub(deadline, now);
+  return gpr_time_to_millis(gpr_time_add(
+      timeout, gpr_time_from_nanos(GPR_NS_PER_MS - 1, GPR_TIMESPAN)));
+}
+
+/*
+ * basic_pollset - a vtable that provides polling for zero or one file
+ *                 descriptor via poll()
+ */
+
+typedef struct grpc_unary_promote_args {
+  const grpc_pollset_vtable *original_vtable;
+  grpc_pollset *pollset;
+  grpc_fd *fd;
+  grpc_closure promotion_closure;
+} grpc_unary_promote_args;
+
+static void basic_do_promote(grpc_exec_ctx *exec_ctx, void *args,
+                             bool success) {
+  grpc_unary_promote_args *up_args = args;
+  const grpc_pollset_vtable *original_vtable = up_args->original_vtable;
+  grpc_pollset *pollset = up_args->pollset;
+  grpc_fd *fd = up_args->fd;
+
+  /*
+   * This is quite tricky. There are a number of cases to keep in mind here:
+   * 1. fd may have been orphaned
+   * 2. The pollset may no longer be a unary poller (and we can't let case #1
+   * leak to other pollset types!)
+   * 3. pollset's fd (which may have changed) may have been orphaned
+   * 4. The pollset may be shutting down.
+   */
+
+  gpr_mu_lock(&pollset->mu);
+  /* First we need to ensure that nobody is polling concurrently */
+  GPR_ASSERT(!pollset_has_workers(pollset));
+
+  gpr_free(up_args);
+  /* At this point the pollset may no longer be a unary poller. In that case
+   * we should just call the right add function and be done. */
+  /* TODO(klempner): If we're not careful this could cause infinite recursion.
+   * That's not a problem for now because empty_pollset has a trivial poller
+   * and we don't have any mechanism to unbecome multipoller. */
+  pollset->in_flight_cbs--;
+  if (pollset->shutting_down) {
+    /* We don't care about this pollset anymore. */
+    if (pollset->in_flight_cbs == 0 && !pollset->called_shutdown) {
+      pollset->called_shutdown = 1;
+      finish_shutdown(exec_ctx, pollset);
+    }
+  } else if (fd_is_orphaned(fd)) {
+    /* Don't try to add it to anything, we'll drop our ref on it below */
+  } else if (pollset->vtable != original_vtable) {
+    pollset->vtable->add_fd(exec_ctx, pollset, fd, 0);
+  } else if (fd != pollset->data.ptr) {
+    grpc_fd *fds[2];
+    fds[0] = pollset->data.ptr;
+    fds[1] = fd;
+
+    if (fds[0] && !fd_is_orphaned(fds[0])) {
+      platform_become_multipoller(exec_ctx, pollset, fds, GPR_ARRAY_SIZE(fds));
+      GRPC_FD_UNREF(fds[0], "basicpoll");
+    } else {
+      /* old fd is orphaned and we haven't cleaned it up until now, so remain a
+       * unary poller */
+      /* Note that it is possible that fds[1] is also orphaned at this point.
+       * That's okay, we'll correct it at the next add or poll. */
+      if (fds[0]) GRPC_FD_UNREF(fds[0], "basicpoll");
+      pollset->data.ptr = fd;
+      GRPC_FD_REF(fd, "basicpoll");
+    }
+  }
+
+  gpr_mu_unlock(&pollset->mu);
+
+  /* Matching ref in basic_pollset_add_fd */
+  GRPC_FD_UNREF(fd, "basicpoll_add");
+}
+
+static void basic_pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                                 grpc_fd *fd, int and_unlock_pollset) {
+  grpc_unary_promote_args *up_args;
+  GPR_ASSERT(fd);
+  if (fd == pollset->data.ptr) goto exit;
+
+  if (!pollset_has_workers(pollset)) {
+    /* Fast path -- no in flight cbs */
+    /* TODO(klempner): Comment this out and fix any test failures or establish
+     * they are due to timing issues */
+    grpc_fd *fds[2];
+    fds[0] = pollset->data.ptr;
+    fds[1] = fd;
+
+    if (fds[0] == NULL) {
+      pollset->data.ptr = fd;
+      GRPC_FD_REF(fd, "basicpoll");
+    } else if (!fd_is_orphaned(fds[0])) {
+      platform_become_multipoller(exec_ctx, pollset, fds, GPR_ARRAY_SIZE(fds));
+      GRPC_FD_UNREF(fds[0], "basicpoll");
+    } else {
+      /* old fd is orphaned and we haven't cleaned it up until now, so remain a
+       * unary poller */
+      GRPC_FD_UNREF(fds[0], "basicpoll");
+      pollset->data.ptr = fd;
+      GRPC_FD_REF(fd, "basicpoll");
+    }
+    goto exit;
+  }
+
+  /* Now we need to promote. This needs to happen when we're not polling. Since
+   * this may be called from poll, the wait needs to happen asynchronously. */
+  GRPC_FD_REF(fd, "basicpoll_add");
+  pollset->in_flight_cbs++;
+  up_args = gpr_malloc(sizeof(*up_args));
+  up_args->fd = fd;
+  up_args->original_vtable = pollset->vtable;
+  up_args->pollset = pollset;
+  up_args->promotion_closure.cb = basic_do_promote;
+  up_args->promotion_closure.cb_arg = up_args;
+
+  grpc_closure_list_add(&pollset->idle_jobs, &up_args->promotion_closure, 1);
+  pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
+
+exit:
+  if (and_unlock_pollset) {
+    gpr_mu_unlock(&pollset->mu);
+  }
+}
+
+static void basic_pollset_maybe_work_and_unlock(grpc_exec_ctx *exec_ctx,
+                                                grpc_pollset *pollset,
+                                                grpc_pollset_worker *worker,
+                                                gpr_timespec deadline,
+                                                gpr_timespec now) {
+#define POLLOUT_CHECK (POLLOUT | POLLHUP | POLLERR)
+#define POLLIN_CHECK (POLLIN | POLLHUP | POLLERR)
+
+  struct pollfd pfd[3];
+  grpc_fd *fd;
+  grpc_fd_watcher fd_watcher;
+  int timeout;
+  int r;
+  nfds_t nfds;
+
+  fd = pollset->data.ptr;
+  if (fd && fd_is_orphaned(fd)) {
+    GRPC_FD_UNREF(fd, "basicpoll");
+    fd = pollset->data.ptr = NULL;
+  }
+  timeout = poll_deadline_to_millis_timeout(deadline, now);
+  pfd[0].fd = GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd);
+  pfd[0].events = POLLIN;
+  pfd[0].revents = 0;
+  pfd[1].fd = GRPC_WAKEUP_FD_GET_READ_FD(&worker->wakeup_fd->fd);
+  pfd[1].events = POLLIN;
+  pfd[1].revents = 0;
+  nfds = 2;
+  if (fd) {
+    pfd[2].fd = fd->fd;
+    pfd[2].revents = 0;
+    GRPC_FD_REF(fd, "basicpoll_begin");
+    gpr_mu_unlock(&pollset->mu);
+    pfd[2].events =
+        (short)fd_begin_poll(fd, pollset, worker, POLLIN, POLLOUT, &fd_watcher);
+    if (pfd[2].events != 0) {
+      nfds++;
+    }
+  } else {
+    gpr_mu_unlock(&pollset->mu);
+  }
+
+  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
+     even going into the blocking annotation if possible */
+  /* poll fd count (argument 2) is shortened by one if we have no events
+     to poll on - such that it only includes the kicker */
+  GPR_TIMER_BEGIN("poll", 0);
+  GRPC_SCHEDULING_START_BLOCKING_REGION;
+  r = grpc_poll_function(pfd, nfds, timeout);
+  GRPC_SCHEDULING_END_BLOCKING_REGION;
+  GPR_TIMER_END("poll", 0);
+
+  if (r < 0) {
+    if (errno != EINTR) {
+      gpr_log(GPR_ERROR, "poll() failed: %s", strerror(errno));
+    }
+    if (fd) {
+      fd_end_poll(exec_ctx, &fd_watcher, 0, 0);
+    }
+  } else if (r == 0) {
+    if (fd) {
+      fd_end_poll(exec_ctx, &fd_watcher, 0, 0);
+    }
+  } else {
+    if (pfd[0].revents & POLLIN_CHECK) {
+      grpc_wakeup_fd_consume_wakeup(&grpc_global_wakeup_fd);
+    }
+    if (pfd[1].revents & POLLIN_CHECK) {
+      grpc_wakeup_fd_consume_wakeup(&worker->wakeup_fd->fd);
+    }
+    if (nfds > 2) {
+      fd_end_poll(exec_ctx, &fd_watcher, pfd[2].revents & POLLIN_CHECK,
+                  pfd[2].revents & POLLOUT_CHECK);
+    } else if (fd) {
+      fd_end_poll(exec_ctx, &fd_watcher, 0, 0);
+    }
+  }
+
+  if (fd) {
+    GRPC_FD_UNREF(fd, "basicpoll_begin");
+  }
+}
+
+static void basic_pollset_destroy(grpc_pollset *pollset) {
+  if (pollset->data.ptr != NULL) {
+    GRPC_FD_UNREF(pollset->data.ptr, "basicpoll");
+    pollset->data.ptr = NULL;
+  }
+}
+
+static const grpc_pollset_vtable basic_pollset = {
+    basic_pollset_add_fd, basic_pollset_maybe_work_and_unlock,
+    basic_pollset_destroy, basic_pollset_destroy};
+
+static void become_basic_pollset(grpc_pollset *pollset, grpc_fd *fd_or_null) {
+  pollset->vtable = &basic_pollset;
+  pollset->data.ptr = fd_or_null;
+  if (fd_or_null != NULL) {
+    GRPC_FD_REF(fd_or_null, "basicpoll");
+  }
+}
+
+/*******************************************************************************
+ * pollset_multipoller_with_poll_posix.c
+ */
+
+#ifndef GPR_LINUX_MULTIPOLL_WITH_EPOLL
+
+typedef struct {
+  /* all polled fds */
+  size_t fd_count;
+  size_t fd_capacity;
+  grpc_fd **fds;
+  /* fds that have been removed from the pollset explicitly */
+  size_t del_count;
+  size_t del_capacity;
+  grpc_fd **dels;
+} poll_hdr;
+
+static void multipoll_with_poll_pollset_add_fd(grpc_exec_ctx *exec_ctx,
+                                               grpc_pollset *pollset,
+                                               grpc_fd *fd,
+                                               int and_unlock_pollset) {
+  size_t i;
+  poll_hdr *h = pollset->data.ptr;
+  /* TODO(ctiller): this is O(num_fds^2); maybe switch to a hash set here */
+  for (i = 0; i < h->fd_count; i++) {
+    if (h->fds[i] == fd) goto exit;
+  }
+  if (h->fd_count == h->fd_capacity) {
+    h->fd_capacity = GPR_MAX(h->fd_capacity + 8, h->fd_count * 3 / 2);
+    h->fds = gpr_realloc(h->fds, sizeof(grpc_fd *) * h->fd_capacity);
+  }
+  h->fds[h->fd_count++] = fd;
+  GRPC_FD_REF(fd, "multipoller");
+exit:
+  if (and_unlock_pollset) {
+    gpr_mu_unlock(&pollset->mu);
+  }
+}
+
+static void multipoll_with_poll_pollset_maybe_work_and_unlock(
+    grpc_exec_ctx *exec_ctx, grpc_pollset *pollset, grpc_pollset_worker *worker,
+    gpr_timespec deadline, gpr_timespec now) {
+#define POLLOUT_CHECK (POLLOUT | POLLHUP | POLLERR)
+#define POLLIN_CHECK (POLLIN | POLLHUP | POLLERR)
+
+  int timeout;
+  int r;
+  size_t i, j, fd_count;
+  nfds_t pfd_count;
+  poll_hdr *h;
+  /* TODO(ctiller): inline some elements to avoid an allocation */
+  grpc_fd_watcher *watchers;
+  struct pollfd *pfds;
+
+  h = pollset->data.ptr;
+  timeout = poll_deadline_to_millis_timeout(deadline, now);
+  /* TODO(ctiller): perform just one malloc here if we exceed the inline case */
+  pfds = gpr_malloc(sizeof(*pfds) * (h->fd_count + 2));
+  watchers = gpr_malloc(sizeof(*watchers) * (h->fd_count + 2));
+  fd_count = 0;
+  pfd_count = 2;
+  pfds[0].fd = GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd);
+  pfds[0].events = POLLIN;
+  pfds[0].revents = 0;
+  pfds[1].fd = GRPC_WAKEUP_FD_GET_READ_FD(&worker->wakeup_fd->fd);
+  pfds[1].events = POLLIN;
+  pfds[1].revents = 0;
+  for (i = 0; i < h->fd_count; i++) {
+    int remove = fd_is_orphaned(h->fds[i]);
+    for (j = 0; !remove && j < h->del_count; j++) {
+      if (h->fds[i] == h->dels[j]) remove = 1;
+    }
+    if (remove) {
+      GRPC_FD_UNREF(h->fds[i], "multipoller");
+    } else {
+      h->fds[fd_count++] = h->fds[i];
+      watchers[pfd_count].fd = h->fds[i];
+      GRPC_FD_REF(watchers[pfd_count].fd, "multipoller_start");
+      pfds[pfd_count].fd = h->fds[i]->fd;
+      pfds[pfd_count].revents = 0;
+      pfd_count++;
+    }
+  }
+  for (j = 0; j < h->del_count; j++) {
+    GRPC_FD_UNREF(h->dels[j], "multipoller_del");
+  }
+  h->del_count = 0;
+  h->fd_count = fd_count;
+  gpr_mu_unlock(&pollset->mu);
+
+  for (i = 2; i < pfd_count; i++) {
+    grpc_fd *fd = watchers[i].fd;
+    pfds[i].events = (short)fd_begin_poll(fd, pollset, worker, POLLIN, POLLOUT,
+                                          &watchers[i]);
+    GRPC_FD_UNREF(fd, "multipoller_start");
+  }
+
+  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
+     even going into the blocking annotation if possible */
+  GRPC_SCHEDULING_START_BLOCKING_REGION;
+  r = grpc_poll_function(pfds, pfd_count, timeout);
+  GRPC_SCHEDULING_END_BLOCKING_REGION;
+
+  if (r < 0) {
+    if (errno != EINTR) {
+      gpr_log(GPR_ERROR, "poll() failed: %s", strerror(errno));
+    }
+    for (i = 2; i < pfd_count; i++) {
+      fd_end_poll(exec_ctx, &watchers[i], 0, 0);
+    }
+  } else if (r == 0) {
+    for (i = 2; i < pfd_count; i++) {
+      fd_end_poll(exec_ctx, &watchers[i], 0, 0);
+    }
+  } else {
+    if (pfds[0].revents & POLLIN_CHECK) {
+      grpc_wakeup_fd_consume_wakeup(&grpc_global_wakeup_fd);
+    }
+    if (pfds[1].revents & POLLIN_CHECK) {
+      grpc_wakeup_fd_consume_wakeup(&worker->wakeup_fd->fd);
+    }
+    for (i = 2; i < pfd_count; i++) {
+      if (watchers[i].fd == NULL) {
+        fd_end_poll(exec_ctx, &watchers[i], 0, 0);
+        continue;
+      }
+      fd_end_poll(exec_ctx, &watchers[i], pfds[i].revents & POLLIN_CHECK,
+                  pfds[i].revents & POLLOUT_CHECK);
+    }
+  }
+
+  gpr_free(pfds);
+  gpr_free(watchers);
+}
+
+static void multipoll_with_poll_pollset_finish_shutdown(grpc_pollset *pollset) {
+  size_t i;
+  poll_hdr *h = pollset->data.ptr;
+  for (i = 0; i < h->fd_count; i++) {
+    GRPC_FD_UNREF(h->fds[i], "multipoller");
+  }
+  for (i = 0; i < h->del_count; i++) {
+    GRPC_FD_UNREF(h->dels[i], "multipoller_del");
+  }
+  h->fd_count = 0;
+  h->del_count = 0;
+}
+
+static void multipoll_with_poll_pollset_destroy(grpc_pollset *pollset) {
+  poll_hdr *h = pollset->data.ptr;
+  multipoll_with_poll_pollset_finish_shutdown(pollset);
+  gpr_free(h->fds);
+  gpr_free(h->dels);
+  gpr_free(h);
+}
+
+static const grpc_pollset_vtable multipoll_with_poll_pollset = {
+    multipoll_with_poll_pollset_add_fd,
+    multipoll_with_poll_pollset_maybe_work_and_unlock,
+    multipoll_with_poll_pollset_finish_shutdown,
+    multipoll_with_poll_pollset_destroy};
+
+static void poll_become_multipoller(grpc_exec_ctx *exec_ctx,
+                                    grpc_pollset *pollset, grpc_fd **fds,
+                                    size_t nfds) {
+  size_t i;
+  poll_hdr *h = gpr_malloc(sizeof(poll_hdr));
+  pollset->vtable = &multipoll_with_poll_pollset;
+  pollset->data.ptr = h;
+  h->fd_count = nfds;
+  h->fd_capacity = nfds;
+  h->fds = gpr_malloc(nfds * sizeof(grpc_fd *));
+  h->del_count = 0;
+  h->del_capacity = 0;
+  h->dels = NULL;
+  for (i = 0; i < nfds; i++) {
+    h->fds[i] = fds[i];
+    GRPC_FD_REF(fds[i], "multipoller");
+  }
+}
+
+#endif /* !GPR_LINUX_MULTIPOLL_WITH_EPOLL */
+
+/*******************************************************************************
+ * pollset_multipoller_with_epoll_posix.c
+ */
+
+#ifdef GPR_LINUX_MULTIPOLL_WITH_EPOLL
+
+#include <errno.h>
+#include <poll.h>
+#include <string.h>
+#include <sys/epoll.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/useful.h>
+
+#include "src/core/lib/iomgr/ev_posix.h"
+#include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/support/block_annotate.h"
+
+static void set_ready(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure **st) {
+  /* only one set_ready can be active at once (but there may be a racing
+     notify_on) */
+  gpr_mu_lock(&fd->mu);
+  set_ready_locked(exec_ctx, fd, st);
+  gpr_mu_unlock(&fd->mu);
+}
+
+static void fd_become_readable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
+  set_ready(exec_ctx, fd, &fd->read_closure);
+}
+
+static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
+  set_ready(exec_ctx, fd, &fd->write_closure);
+}
+
+struct epoll_fd_list {
+  int *epoll_fds;
+  size_t count;
+  size_t capacity;
+};
+
+static struct epoll_fd_list epoll_fd_global_list;
+static gpr_once init_epoll_fd_list_mu = GPR_ONCE_INIT;
+static gpr_mu epoll_fd_list_mu;
+
+static void init_mu(void) { gpr_mu_init(&epoll_fd_list_mu); }
+
+static void add_epoll_fd_to_global_list(int epoll_fd) {
+  gpr_once_init(&init_epoll_fd_list_mu, init_mu);
+
+  gpr_mu_lock(&epoll_fd_list_mu);
+  if (epoll_fd_global_list.count == epoll_fd_global_list.capacity) {
+    epoll_fd_global_list.capacity =
+        GPR_MAX((size_t)8, epoll_fd_global_list.capacity * 2);
+    epoll_fd_global_list.epoll_fds =
+        gpr_realloc(epoll_fd_global_list.epoll_fds,
+                    epoll_fd_global_list.capacity * sizeof(int));
+  }
+  epoll_fd_global_list.epoll_fds[epoll_fd_global_list.count++] = epoll_fd;
+  gpr_mu_unlock(&epoll_fd_list_mu);
+}
+
+static void remove_epoll_fd_from_global_list(int epoll_fd) {
+  gpr_mu_lock(&epoll_fd_list_mu);
+  GPR_ASSERT(epoll_fd_global_list.count > 0);
+  for (size_t i = 0; i < epoll_fd_global_list.count; i++) {
+    if (epoll_fd == epoll_fd_global_list.epoll_fds[i]) {
+      epoll_fd_global_list.epoll_fds[i] =
+          epoll_fd_global_list.epoll_fds[--(epoll_fd_global_list.count)];
+      break;
+    }
+  }
+  gpr_mu_unlock(&epoll_fd_list_mu);
+}
+
+static void remove_fd_from_all_epoll_sets(int fd) {
+  int err;
+  gpr_once_init(&init_epoll_fd_list_mu, init_mu);
+  gpr_mu_lock(&epoll_fd_list_mu);
+  if (epoll_fd_global_list.count == 0) {
+    gpr_mu_unlock(&epoll_fd_list_mu);
+    return;
+  }
+  for (size_t i = 0; i < epoll_fd_global_list.count; i++) {
+    err = epoll_ctl(epoll_fd_global_list.epoll_fds[i], EPOLL_CTL_DEL, fd, NULL);
+    if (err < 0 && errno != ENOENT) {
+      gpr_log(GPR_ERROR, "epoll_ctl del for %d failed: %s", fd,
+              strerror(errno));
+    }
+  }
+  gpr_mu_unlock(&epoll_fd_list_mu);
+}
+
+typedef struct {
+  grpc_pollset *pollset;
+  grpc_fd *fd;
+  grpc_closure closure;
+} delayed_add;
+
+typedef struct { int epoll_fd; } epoll_hdr;
+
+static void finally_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           grpc_fd *fd) {
+  epoll_hdr *h = pollset->data.ptr;
+  struct epoll_event ev;
+  int err;
+  grpc_fd_watcher watcher;
+
+  /* We pretend to be polling whilst adding an fd to keep the fd from being
+     closed during the add. This may result in a spurious wakeup being assigned
+     to this pollset whilst adding, but that should be benign. */
+  GPR_ASSERT(fd_begin_poll(fd, pollset, NULL, 0, 0, &watcher) == 0);
+  if (watcher.fd != NULL) {
+    ev.events = (uint32_t)(EPOLLIN | EPOLLOUT | EPOLLET);
+    ev.data.ptr = fd;
+    err = epoll_ctl(h->epoll_fd, EPOLL_CTL_ADD, fd->fd, &ev);
+    if (err < 0) {
+      /* FDs may be added to a pollset multiple times, so EEXIST is normal. */
+      if (errno != EEXIST) {
+        gpr_log(GPR_ERROR, "epoll_ctl add for %d failed: %s", fd->fd,
+                strerror(errno));
+      }
+    }
+  }
+  fd_end_poll(exec_ctx, &watcher, 0, 0);
+}
+
+static void perform_delayed_add(grpc_exec_ctx *exec_ctx, void *arg,
+                                bool iomgr_status) {
+  delayed_add *da = arg;
+
+  if (!fd_is_orphaned(da->fd)) {
+    finally_add_fd(exec_ctx, da->pollset, da->fd);
+  }
+
+  gpr_mu_lock(&da->pollset->mu);
+  da->pollset->in_flight_cbs--;
+  if (da->pollset->shutting_down) {
+    /* We don't care about this pollset anymore. */
+    if (da->pollset->in_flight_cbs == 0 && !da->pollset->called_shutdown) {
+      da->pollset->called_shutdown = 1;
+      grpc_exec_ctx_enqueue(exec_ctx, da->pollset->shutdown_done, true, NULL);
+    }
+  }
+  gpr_mu_unlock(&da->pollset->mu);
+
+  GRPC_FD_UNREF(da->fd, "delayed_add");
+
+  gpr_free(da);
+}
+
+static void multipoll_with_epoll_pollset_add_fd(grpc_exec_ctx *exec_ctx,
+                                                grpc_pollset *pollset,
+                                                grpc_fd *fd,
+                                                int and_unlock_pollset) {
+  if (and_unlock_pollset) {
+    gpr_mu_unlock(&pollset->mu);
+    finally_add_fd(exec_ctx, pollset, fd);
+  } else {
+    delayed_add *da = gpr_malloc(sizeof(*da));
+    da->pollset = pollset;
+    da->fd = fd;
+    GRPC_FD_REF(fd, "delayed_add");
+    grpc_closure_init(&da->closure, perform_delayed_add, da);
+    pollset->in_flight_cbs++;
+    grpc_exec_ctx_enqueue(exec_ctx, &da->closure, true, NULL);
+  }
+}
+
+/* TODO(klempner): We probably want to turn this down a bit */
+#define GRPC_EPOLL_MAX_EVENTS 1000
+
+static void multipoll_with_epoll_pollset_maybe_work_and_unlock(
+    grpc_exec_ctx *exec_ctx, grpc_pollset *pollset, grpc_pollset_worker *worker,
+    gpr_timespec deadline, gpr_timespec now) {
+  struct epoll_event ep_ev[GRPC_EPOLL_MAX_EVENTS];
+  int ep_rv;
+  int poll_rv;
+  epoll_hdr *h = pollset->data.ptr;
+  int timeout_ms;
+  struct pollfd pfds[2];
+
+  /* If you want to ignore epoll's ability to sanely handle parallel pollers,
+   * for a more apples-to-apples performance comparison with poll, add a
+   * if (pollset->counter != 0) { return 0; }
+   * here.
+   */
+
+  gpr_mu_unlock(&pollset->mu);
+
+  timeout_ms = poll_deadline_to_millis_timeout(deadline, now);
+
+  pfds[0].fd = GRPC_WAKEUP_FD_GET_READ_FD(&worker->wakeup_fd->fd);
+  pfds[0].events = POLLIN;
+  pfds[0].revents = 0;
+  pfds[1].fd = h->epoll_fd;
+  pfds[1].events = POLLIN;
+  pfds[1].revents = 0;
+
+  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
+     even going into the blocking annotation if possible */
+  GPR_TIMER_BEGIN("poll", 0);
+  GRPC_SCHEDULING_START_BLOCKING_REGION;
+  poll_rv = grpc_poll_function(pfds, 2, timeout_ms);
+  GRPC_SCHEDULING_END_BLOCKING_REGION;
+  GPR_TIMER_END("poll", 0);
+
+  if (poll_rv < 0) {
+    if (errno != EINTR) {
+      gpr_log(GPR_ERROR, "poll() failed: %s", strerror(errno));
+    }
+  } else if (poll_rv == 0) {
+    /* do nothing */
+  } else {
+    if (pfds[0].revents) {
+      grpc_wakeup_fd_consume_wakeup(&worker->wakeup_fd->fd);
+    }
+    if (pfds[1].revents) {
+      do {
+        /* The following epoll_wait never blocks; it has a timeout of 0 */
+        ep_rv = epoll_wait(h->epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, 0);
+        if (ep_rv < 0) {
+          if (errno != EINTR) {
+            gpr_log(GPR_ERROR, "epoll_wait() failed: %s", strerror(errno));
+          }
+        } else {
+          int i;
+          for (i = 0; i < ep_rv; ++i) {
+            grpc_fd *fd = ep_ev[i].data.ptr;
+            /* TODO(klempner): We might want to consider making err and pri
+             * separate events */
+            int cancel = ep_ev[i].events & (EPOLLERR | EPOLLHUP);
+            int read_ev = ep_ev[i].events & (EPOLLIN | EPOLLPRI);
+            int write_ev = ep_ev[i].events & EPOLLOUT;
+            if (fd == NULL) {
+              grpc_wakeup_fd_consume_wakeup(&grpc_global_wakeup_fd);
+            } else {
+              if (read_ev || cancel) {
+                fd_become_readable(exec_ctx, fd);
+              }
+              if (write_ev || cancel) {
+                fd_become_writable(exec_ctx, fd);
+              }
+            }
+          }
+        }
+      } while (ep_rv == GRPC_EPOLL_MAX_EVENTS);
+    }
+  }
+}
+
+static void multipoll_with_epoll_pollset_finish_shutdown(
+    grpc_pollset *pollset) {}
+
+static void multipoll_with_epoll_pollset_destroy(grpc_pollset *pollset) {
+  epoll_hdr *h = pollset->data.ptr;
+  close(h->epoll_fd);
+  remove_epoll_fd_from_global_list(h->epoll_fd);
+  gpr_free(h);
+}
+
+static const grpc_pollset_vtable multipoll_with_epoll_pollset = {
+    multipoll_with_epoll_pollset_add_fd,
+    multipoll_with_epoll_pollset_maybe_work_and_unlock,
+    multipoll_with_epoll_pollset_finish_shutdown,
+    multipoll_with_epoll_pollset_destroy};
+
+static void epoll_become_multipoller(grpc_exec_ctx *exec_ctx,
+                                     grpc_pollset *pollset, grpc_fd **fds,
+                                     size_t nfds) {
+  size_t i;
+  epoll_hdr *h = gpr_malloc(sizeof(epoll_hdr));
+  struct epoll_event ev;
+  int err;
+
+  pollset->vtable = &multipoll_with_epoll_pollset;
+  pollset->data.ptr = h;
+  h->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
+  if (h->epoll_fd < 0) {
+    /* TODO(klempner): Fall back to poll here, especially on ENOSYS */
+    gpr_log(GPR_ERROR, "epoll_create1 failed: %s", strerror(errno));
+    abort();
+  }
+  add_epoll_fd_to_global_list(h->epoll_fd);
+
+  ev.events = (uint32_t)(EPOLLIN | EPOLLET);
+  ev.data.ptr = NULL;
+  err = epoll_ctl(h->epoll_fd, EPOLL_CTL_ADD,
+                  GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd), &ev);
+  if (err < 0) {
+    gpr_log(GPR_ERROR, "epoll_ctl add for %d failed: %s",
+            GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd),
+            strerror(errno));
+  }
+
+  for (i = 0; i < nfds; i++) {
+    multipoll_with_epoll_pollset_add_fd(exec_ctx, pollset, fds[i], 0);
+  }
+}
+
+#else /* GPR_LINUX_MULTIPOLL_WITH_EPOLL */
+
+static void remove_fd_from_all_epoll_sets(int fd) {}
+
+#endif /* GPR_LINUX_MULTIPOLL_WITH_EPOLL */
+
+/*******************************************************************************
+ * pollset_set_posix.c
+ */
+
+static grpc_pollset_set *pollset_set_create(void) {
+  grpc_pollset_set *pollset_set = gpr_malloc(sizeof(*pollset_set));
+  memset(pollset_set, 0, sizeof(*pollset_set));
+  gpr_mu_init(&pollset_set->mu);
+  return pollset_set;
+}
+
+static void pollset_set_destroy(grpc_pollset_set *pollset_set) {
+  size_t i;
+  gpr_mu_destroy(&pollset_set->mu);
+  for (i = 0; i < pollset_set->fd_count; i++) {
+    GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
+  }
+  gpr_free(pollset_set->pollsets);
+  gpr_free(pollset_set->pollset_sets);
+  gpr_free(pollset_set->fds);
+  gpr_free(pollset_set);
+}
+
+static void pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
+                                    grpc_pollset_set *pollset_set,
+                                    grpc_pollset *pollset) {
+  size_t i, j;
+  gpr_mu_lock(&pollset_set->mu);
+  if (pollset_set->pollset_count == pollset_set->pollset_capacity) {
+    pollset_set->pollset_capacity =
+        GPR_MAX(8, 2 * pollset_set->pollset_capacity);
+    pollset_set->pollsets =
+        gpr_realloc(pollset_set->pollsets, pollset_set->pollset_capacity *
+                                               sizeof(*pollset_set->pollsets));
+  }
+  pollset_set->pollsets[pollset_set->pollset_count++] = pollset;
+  for (i = 0, j = 0; i < pollset_set->fd_count; i++) {
+    if (fd_is_orphaned(pollset_set->fds[i])) {
+      GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
+    } else {
+      pollset_add_fd(exec_ctx, pollset, pollset_set->fds[i]);
+      pollset_set->fds[j++] = pollset_set->fds[i];
+    }
+  }
+  pollset_set->fd_count = j;
+  gpr_mu_unlock(&pollset_set->mu);
+}
+
+static void pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
+                                    grpc_pollset_set *pollset_set,
+                                    grpc_pollset *pollset) {
+  size_t i;
+  gpr_mu_lock(&pollset_set->mu);
+  for (i = 0; i < pollset_set->pollset_count; i++) {
+    if (pollset_set->pollsets[i] == pollset) {
+      pollset_set->pollset_count--;
+      GPR_SWAP(grpc_pollset *, pollset_set->pollsets[i],
+               pollset_set->pollsets[pollset_set->pollset_count]);
+      break;
+    }
+  }
+  gpr_mu_unlock(&pollset_set->mu);
+}
+
+static void pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
+                                        grpc_pollset_set *bag,
+                                        grpc_pollset_set *item) {
+  size_t i, j;
+  gpr_mu_lock(&bag->mu);
+  if (bag->pollset_set_count == bag->pollset_set_capacity) {
+    bag->pollset_set_capacity = GPR_MAX(8, 2 * bag->pollset_set_capacity);
+    bag->pollset_sets =
+        gpr_realloc(bag->pollset_sets,
+                    bag->pollset_set_capacity * sizeof(*bag->pollset_sets));
+  }
+  bag->pollset_sets[bag->pollset_set_count++] = item;
+  for (i = 0, j = 0; i < bag->fd_count; i++) {
+    if (fd_is_orphaned(bag->fds[i])) {
+      GRPC_FD_UNREF(bag->fds[i], "pollset_set");
+    } else {
+      pollset_set_add_fd(exec_ctx, item, bag->fds[i]);
+      bag->fds[j++] = bag->fds[i];
+    }
+  }
+  bag->fd_count = j;
+  gpr_mu_unlock(&bag->mu);
+}
+
+static void pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
+                                        grpc_pollset_set *bag,
+                                        grpc_pollset_set *item) {
+  size_t i;
+  gpr_mu_lock(&bag->mu);
+  for (i = 0; i < bag->pollset_set_count; i++) {
+    if (bag->pollset_sets[i] == item) {
+      bag->pollset_set_count--;
+      GPR_SWAP(grpc_pollset_set *, bag->pollset_sets[i],
+               bag->pollset_sets[bag->pollset_set_count]);
+      break;
+    }
+  }
+  gpr_mu_unlock(&bag->mu);
+}
+
+static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
+                               grpc_pollset_set *pollset_set, grpc_fd *fd) {
+  size_t i;
+  gpr_mu_lock(&pollset_set->mu);
+  if (pollset_set->fd_count == pollset_set->fd_capacity) {
+    pollset_set->fd_capacity = GPR_MAX(8, 2 * pollset_set->fd_capacity);
+    pollset_set->fds = gpr_realloc(
+        pollset_set->fds, pollset_set->fd_capacity * sizeof(*pollset_set->fds));
+  }
+  GRPC_FD_REF(fd, "pollset_set");
+  pollset_set->fds[pollset_set->fd_count++] = fd;
+  for (i = 0; i < pollset_set->pollset_count; i++) {
+    pollset_add_fd(exec_ctx, pollset_set->pollsets[i], fd);
+  }
+  for (i = 0; i < pollset_set->pollset_set_count; i++) {
+    pollset_set_add_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
+  }
+  gpr_mu_unlock(&pollset_set->mu);
+}
+
+static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
+                               grpc_pollset_set *pollset_set, grpc_fd *fd) {
+  size_t i;
+  gpr_mu_lock(&pollset_set->mu);
+  for (i = 0; i < pollset_set->fd_count; i++) {
+    if (pollset_set->fds[i] == fd) {
+      pollset_set->fd_count--;
+      GPR_SWAP(grpc_fd *, pollset_set->fds[i],
+               pollset_set->fds[pollset_set->fd_count]);
+      GRPC_FD_UNREF(fd, "pollset_set");
+      break;
+    }
+  }
+  for (i = 0; i < pollset_set->pollset_set_count; i++) {
+    pollset_set_del_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
+  }
+  gpr_mu_unlock(&pollset_set->mu);
+}
+
+/*******************************************************************************
+ * event engine binding
+ */
+
+static void shutdown_engine(void) {
+  fd_global_shutdown();
+  pollset_global_shutdown();
+}
+
+static const grpc_event_engine_vtable vtable = {
+    .pollset_size = sizeof(grpc_pollset),
+
+    .fd_create = fd_create,
+    .fd_wrapped_fd = fd_wrapped_fd,
+    .fd_orphan = fd_orphan,
+    .fd_shutdown = fd_shutdown,
+    .fd_notify_on_read = fd_notify_on_read,
+    .fd_notify_on_write = fd_notify_on_write,
+
+    .pollset_init = pollset_init,
+    .pollset_shutdown = pollset_shutdown,
+    .pollset_reset = pollset_reset,
+    .pollset_destroy = pollset_destroy,
+    .pollset_work = pollset_work,
+    .pollset_kick = pollset_kick,
+    .pollset_add_fd = pollset_add_fd,
+
+    .pollset_set_create = pollset_set_create,
+    .pollset_set_destroy = pollset_set_destroy,
+    .pollset_set_add_pollset = pollset_set_add_pollset,
+    .pollset_set_del_pollset = pollset_set_del_pollset,
+    .pollset_set_add_pollset_set = pollset_set_add_pollset_set,
+    .pollset_set_del_pollset_set = pollset_set_del_pollset_set,
+    .pollset_set_add_fd = pollset_set_add_fd,
+    .pollset_set_del_fd = pollset_set_del_fd,
+
+    .kick_poller = kick_poller,
+
+    .shutdown_engine = shutdown_engine,
+};
+
+const grpc_event_engine_vtable *grpc_init_poll_and_epoll_posix(void) {
+#ifdef GPR_LINUX_MULTIPOLL_WITH_EPOLL
+  platform_become_multipoller = epoll_become_multipoller;
+#else
+  platform_become_multipoller = poll_become_multipoller;
+#endif
+  fd_global_init();
+  pollset_global_init();
+  return &vtable;
+}
+
+#endif
diff --git a/src/core/lib/iomgr/ev_poll_and_epoll_posix.h b/src/core/lib/iomgr/ev_poll_and_epoll_posix.h
new file mode 100644
index 0000000000..4ca371f4f5
--- /dev/null
+++ b/src/core/lib/iomgr/ev_poll_and_epoll_posix.h
@@ -0,0 +1,41 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_IOMGR_EV_POLL_AND_EPOLL_POSIX_H
+#define GRPC_CORE_IOMGR_EV_POLL_AND_EPOLL_POSIX_H
+
+#include "src/core/lib/iomgr/ev_posix.h"
+
+const grpc_event_engine_vtable *grpc_init_poll_and_epoll_posix(void);
+
+#endif /* GRPC_CORE_IOMGR_EV_POLL_AND_EPOLL_POSIX_H */
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
new file mode 100644
index 0000000000..0d16d6ac38
--- /dev/null
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -0,0 +1,159 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/ev_posix.h"
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/iomgr/ev_poll_and_epoll_posix.h"
+
+static const grpc_event_engine_vtable *g_event_engine;
+
+grpc_poll_function_type grpc_poll_function = poll;
+grpc_wakeup_fd grpc_global_wakeup_fd;
+
+void grpc_event_engine_init(void) {
+  if ((g_event_engine = grpc_init_poll_and_epoll_posix())) {
+    return;
+  }
+  gpr_log(GPR_ERROR, "No event engine could be initialized");
+  abort();
+}
+
+void grpc_event_engine_shutdown(void) { g_event_engine->shutdown_engine(); }
+
+grpc_fd *grpc_fd_create(int fd, const char *name) {
+  return g_event_engine->fd_create(fd, name);
+}
+
+int grpc_fd_wrapped_fd(grpc_fd *fd) {
+  return g_event_engine->fd_wrapped_fd(fd);
+}
+
+void grpc_fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure *on_done,
+                    int *release_fd, const char *reason) {
+  g_event_engine->fd_orphan(exec_ctx, fd, on_done, release_fd, reason);
+}
+
+void grpc_fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
+  g_event_engine->fd_shutdown(exec_ctx, fd);
+}
+
+void grpc_fd_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                            grpc_closure *closure) {
+  g_event_engine->fd_notify_on_read(exec_ctx, fd, closure);
+}
+
+void grpc_fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                             grpc_closure *closure) {
+  g_event_engine->fd_notify_on_write(exec_ctx, fd, closure);
+}
+
+size_t grpc_pollset_size(void) { return g_event_engine->pollset_size; }
+
+void grpc_pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
+  g_event_engine->pollset_init(pollset, mu);
+}
+
+void grpc_pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           grpc_closure *closure) {
+  g_event_engine->pollset_shutdown(exec_ctx, pollset, closure);
+}
+
+void grpc_pollset_reset(grpc_pollset *pollset) {
+  g_event_engine->pollset_reset(pollset);
+}
+
+void grpc_pollset_destroy(grpc_pollset *pollset) {
+  g_event_engine->pollset_destroy(pollset);
+}
+
+void grpc_pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                       grpc_pollset_worker **worker, gpr_timespec now,
+                       gpr_timespec deadline) {
+  g_event_engine->pollset_work(exec_ctx, pollset, worker, now, deadline);
+}
+
+void grpc_pollset_kick(grpc_pollset *pollset,
+                       grpc_pollset_worker *specific_worker) {
+  g_event_engine->pollset_kick(pollset, specific_worker);
+}
+
+void grpc_pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                         struct grpc_fd *fd) {
+  g_event_engine->pollset_add_fd(exec_ctx, pollset, fd);
+}
+
+grpc_pollset_set *grpc_pollset_set_create(void) {
+  return g_event_engine->pollset_set_create();
+}
+
+void grpc_pollset_set_destroy(grpc_pollset_set *pollset_set) {
+  g_event_engine->pollset_set_destroy(pollset_set);
+}
+
+void grpc_pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset) {
+  g_event_engine->pollset_set_add_pollset(exec_ctx, pollset_set, pollset);
+}
+
+void grpc_pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset) {
+  g_event_engine->pollset_set_del_pollset(exec_ctx, pollset_set, pollset);
+}
+
+void grpc_pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item) {
+  g_event_engine->pollset_set_add_pollset_set(exec_ctx, bag, item);
+}
+
+void grpc_pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item) {
+  g_event_engine->pollset_set_del_pollset_set(exec_ctx, bag, item);
+}
+
+void grpc_pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
+                             grpc_pollset_set *pollset_set, grpc_fd *fd) {
+  g_event_engine->pollset_set_add_fd(exec_ctx, pollset_set, fd);
+}
+
+void grpc_pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
+                             grpc_pollset_set *pollset_set, grpc_fd *fd) {
+  g_event_engine->pollset_set_del_fd(exec_ctx, pollset_set, fd);
+}
+
+void grpc_kick_poller(void) { g_event_engine->kick_poller(); }
diff --git a/src/core/lib/iomgr/ev_posix.h b/src/core/lib/iomgr/ev_posix.h
new file mode 100644
index 0000000000..8c909f1a3f
--- /dev/null
+++ b/src/core/lib/iomgr/ev_posix.h
@@ -0,0 +1,158 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_IOMGR_EV_POSIX_H
+#define GRPC_CORE_IOMGR_EV_POSIX_H
+
+#include <poll.h>
+
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/pollset.h"
+#include "src/core/lib/iomgr/pollset_set.h"
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+
+typedef struct grpc_fd grpc_fd;
+
+typedef struct grpc_event_engine_vtable {
+  size_t pollset_size;
+
+  grpc_fd *(*fd_create)(int fd, const char *name);
+  int (*fd_wrapped_fd)(grpc_fd *fd);
+  void (*fd_orphan)(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure *on_done,
+                    int *release_fd, const char *reason);
+  void (*fd_shutdown)(grpc_exec_ctx *exec_ctx, grpc_fd *fd);
+  void (*fd_notify_on_read)(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                            grpc_closure *closure);
+  void (*fd_notify_on_write)(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                             grpc_closure *closure);
+
+  void (*pollset_init)(grpc_pollset *pollset, gpr_mu **mu);
+  void (*pollset_shutdown)(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           grpc_closure *closure);
+  void (*pollset_reset)(grpc_pollset *pollset);
+  void (*pollset_destroy)(grpc_pollset *pollset);
+  void (*pollset_work)(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                       grpc_pollset_worker **worker, gpr_timespec now,
+                       gpr_timespec deadline);
+  void (*pollset_kick)(grpc_pollset *pollset,
+                       grpc_pollset_worker *specific_worker);
+  void (*pollset_add_fd)(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                         struct grpc_fd *fd);
+
+  grpc_pollset_set *(*pollset_set_create)(void);
+  void (*pollset_set_destroy)(grpc_pollset_set *pollset_set);
+  void (*pollset_set_add_pollset)(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset);
+  void (*pollset_set_del_pollset)(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset);
+  void (*pollset_set_add_pollset_set)(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item);
+  void (*pollset_set_del_pollset_set)(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item);
+  void (*pollset_set_add_fd)(grpc_exec_ctx *exec_ctx,
+                             grpc_pollset_set *pollset_set, grpc_fd *fd);
+  void (*pollset_set_del_fd)(grpc_exec_ctx *exec_ctx,
+                             grpc_pollset_set *pollset_set, grpc_fd *fd);
+
+  void (*kick_poller)(void);
+
+  void (*shutdown_engine)(void);
+} grpc_event_engine_vtable;
+
+void grpc_event_engine_init(void);
+void grpc_event_engine_shutdown(void);
+
+/* Create a wrapped file descriptor.
+   Requires fd is a non-blocking file descriptor.
+   This takes ownership of closing fd. */
+grpc_fd *grpc_fd_create(int fd, const char *name);
+
+/* Return the wrapped fd, or -1 if it has been released or closed. */
+int grpc_fd_wrapped_fd(grpc_fd *fd);
+
+/* Releases fd to be asynchronously destroyed.
+   on_done is called when the underlying file descriptor is definitely close()d.
+   If on_done is NULL, no callback will be made.
+   If release_fd is not NULL, it's set to fd and fd will not be closed.
+   Requires: *fd initialized; no outstanding notify_on_read or
+   notify_on_write.
+   MUST NOT be called with a pollset lock taken */
+void grpc_fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure *on_done,
+                    int *release_fd, const char *reason);
+
+/* Cause any current callbacks to error out with GRPC_CALLBACK_CANCELLED. */
+void grpc_fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd);
+
+/* Register read interest, causing read_cb to be called once when fd becomes
+   readable, on deadline specified by deadline, or on shutdown triggered by
+   grpc_fd_shutdown.
+   read_cb will be called with read_cb_arg when *fd becomes readable.
+   read_cb is Called with status of GRPC_CALLBACK_SUCCESS if readable,
+   GRPC_CALLBACK_TIMED_OUT if the call timed out,
+   and CANCELLED if the call was cancelled.
+
+   Requires:This method must not be called before the read_cb for any previous
+   call runs. Edge triggered events are used whenever they are supported by the
+   underlying platform. This means that users must drain fd in read_cb before
+   calling notify_on_read again. Users are also expected to handle spurious
+   events, i.e read_cb is called while nothing can be readable from fd  */
+void grpc_fd_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                            grpc_closure *closure);
+
+/* Exactly the same semantics as above, except based on writable events.  */
+void grpc_fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                             grpc_closure *closure);
+
+/* pollset_posix functions */
+
+/* Add an fd to a pollset */
+void grpc_pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                         struct grpc_fd *fd);
+
+/* pollset_set_posix functions */
+
+void grpc_pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
+                             grpc_pollset_set *pollset_set, grpc_fd *fd);
+void grpc_pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
+                             grpc_pollset_set *pollset_set, grpc_fd *fd);
+
+/* override to allow tests to hook poll() usage */
+typedef int (*grpc_poll_function_type)(struct pollfd *, nfds_t, int);
+extern grpc_poll_function_type grpc_poll_function;
+extern grpc_wakeup_fd grpc_global_wakeup_fd;
+
+#endif /* GRPC_CORE_IOMGR_EV_POSIX_H */
diff --git a/src/core/lib/iomgr/exec_ctx.c b/src/core/lib/iomgr/exec_ctx.c
new file mode 100644
index 0000000000..1ed6da623a
--- /dev/null
+++ b/src/core/lib/iomgr/exec_ctx.c
@@ -0,0 +1,151 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/exec_ctx.h"
+
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd.h>
+
+#include "src/core/lib/profiling/timers.h"
+
+#ifndef GRPC_EXECUTION_CONTEXT_SANITIZER
+bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) {
+  bool did_something = 0;
+  GPR_TIMER_BEGIN("grpc_exec_ctx_flush", 0);
+  while (!grpc_closure_list_empty(exec_ctx->closure_list)) {
+    grpc_closure *c = exec_ctx->closure_list.head;
+    exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
+    while (c != NULL) {
+      bool success = (bool)(c->final_data & 1);
+      grpc_closure *next = (grpc_closure *)(c->final_data & ~(uintptr_t)1);
+      did_something = true;
+      GPR_TIMER_BEGIN("grpc_exec_ctx_flush.cb", 0);
+      c->cb(exec_ctx, c->cb_arg, success);
+      GPR_TIMER_END("grpc_exec_ctx_flush.cb", 0);
+      c = next;
+    }
+  }
+  GPR_TIMER_END("grpc_exec_ctx_flush", 0);
+  return did_something;
+}
+
+void grpc_exec_ctx_finish(grpc_exec_ctx *exec_ctx) {
+  grpc_exec_ctx_flush(exec_ctx);
+}
+
+void grpc_exec_ctx_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
+                           bool success,
+                           grpc_workqueue *offload_target_or_null) {
+  GPR_ASSERT(offload_target_or_null == NULL);
+  grpc_closure_list_add(&exec_ctx->closure_list, closure, success);
+}
+
+void grpc_exec_ctx_enqueue_list(grpc_exec_ctx *exec_ctx,
+                                grpc_closure_list *list,
+                                grpc_workqueue *offload_target_or_null) {
+  GPR_ASSERT(offload_target_or_null == NULL);
+  grpc_closure_list_move(list, &exec_ctx->closure_list);
+}
+
+void grpc_exec_ctx_global_init(void) {}
+void grpc_exec_ctx_global_shutdown(void) {}
+#else
+static gpr_mu g_mu;
+static gpr_cv g_cv;
+static int g_threads = 0;
+
+static void run_closure(void *arg) {
+  grpc_closure *closure = arg;
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  closure->cb(&exec_ctx, closure->cb_arg, (closure->final_data & 1) != 0);
+  grpc_exec_ctx_finish(&exec_ctx);
+  gpr_mu_lock(&g_mu);
+  if (--g_threads == 0) {
+    gpr_cv_signal(&g_cv);
+  }
+  gpr_mu_unlock(&g_mu);
+}
+
+static void start_closure(grpc_closure *closure) {
+  gpr_thd_id id;
+  gpr_mu_lock(&g_mu);
+  g_threads++;
+  gpr_mu_unlock(&g_mu);
+  gpr_thd_new(&id, run_closure, closure, NULL);
+}
+
+bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) { return false; }
+
+void grpc_exec_ctx_finish(grpc_exec_ctx *exec_ctx) {}
+
+void grpc_exec_ctx_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
+                           bool success,
+                           grpc_workqueue *offload_target_or_null) {
+  GPR_ASSERT(offload_target_or_null == NULL);
+  if (closure == NULL) return;
+  closure->final_data = success;
+  start_closure(closure);
+}
+
+void grpc_exec_ctx_enqueue_list(grpc_exec_ctx *exec_ctx,
+                                grpc_closure_list *list,
+                                grpc_workqueue *offload_target_or_null) {
+  GPR_ASSERT(offload_target_or_null == NULL);
+  if (list == NULL) return;
+  grpc_closure *p = list->head;
+  while (p) {
+    grpc_closure *start = p;
+    p = grpc_closure_next(start);
+    start_closure(start);
+  }
+  grpc_closure_list r = GRPC_CLOSURE_LIST_INIT;
+  *list = r;
+}
+
+void grpc_exec_ctx_global_init(void) {
+  gpr_mu_init(&g_mu);
+  gpr_cv_init(&g_cv);
+}
+
+void grpc_exec_ctx_global_shutdown(void) {
+  gpr_mu_lock(&g_mu);
+  while (g_threads != 0) {
+    gpr_cv_wait(&g_cv, &g_mu, gpr_inf_future(GPR_CLOCK_REALTIME));
+  }
+  gpr_mu_unlock(&g_mu);
+
+  gpr_mu_destroy(&g_mu);
+  gpr_cv_destroy(&g_cv);
+}
+#endif
diff --git a/src/core/lib/iomgr/exec_ctx.h b/src/core/lib/iomgr/exec_ctx.h
new file mode 100644
index 0000000000..e62ea2dedf
--- /dev/null
+++ b/src/core/lib/iomgr/exec_ctx.h
@@ -0,0 +1,98 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_EXEC_CTX_H
+#define GRPC_CORE_LIB_IOMGR_EXEC_CTX_H
+
+#include "src/core/lib/iomgr/closure.h"
+
+/* #define GRPC_EXECUTION_CONTEXT_SANITIZER 1 */
+
+/** A workqueue represents a list of work to be executed asynchronously.
+    Forward declared here to avoid a circular dependency with workqueue.h. */
+struct grpc_workqueue;
+typedef struct grpc_workqueue grpc_workqueue;
+
+#ifndef GRPC_EXECUTION_CONTEXT_SANITIZER
+/** Execution context.
+ *  A bag of data that collects information along a callstack.
+ *  Generally created at public API entry points, and passed down as
+ *  pointer to child functions that manipulate it.
+ *
+ *  Specific responsibilities (this may grow in the future):
+ *  - track a list of work that needs to be delayed until the top of the
+ *    call stack (this provides a convenient mechanism to run callbacks
+ *    without worrying about locking issues)
+ *
+ *  CONVENTIONS:
+ *  Instance of this must ALWAYS be constructed on the stack, never
+ *  heap allocated. Instances and pointers to them must always be called
+ *  exec_ctx. Instances are always passed as the first argument
+ *  to a function that takes it, and always as a pointer (grpc_exec_ctx
+ *  is never copied).
+ */
+struct grpc_exec_ctx {
+  grpc_closure_list closure_list;
+};
+
+#define GRPC_EXEC_CTX_INIT \
+  { GRPC_CLOSURE_LIST_INIT }
+#else
+struct grpc_exec_ctx {
+  int unused;
+};
+#define GRPC_EXEC_CTX_INIT \
+  { 0 }
+#endif
+
+/** Flush any work that has been enqueued onto this grpc_exec_ctx.
+ *  Caller must guarantee that no interfering locks are held.
+ *  Returns true if work was performed, false otherwise. */
+bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx);
+/** Finish any pending work for a grpc_exec_ctx. Must be called before
+ *  the instance is destroyed, or work may be lost. */
+void grpc_exec_ctx_finish(grpc_exec_ctx *exec_ctx);
+/** Add a closure to be executed at the next flush/finish point */
+void grpc_exec_ctx_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
+                           bool success,
+                           grpc_workqueue *offload_target_or_null);
+/** Add a list of closures to be executed at the next flush/finish point.
+ *  Leaves \a list empty. */
+void grpc_exec_ctx_enqueue_list(grpc_exec_ctx *exec_ctx,
+                                grpc_closure_list *list,
+                                grpc_workqueue *offload_target_or_null);
+
+void grpc_exec_ctx_global_init(void);
+void grpc_exec_ctx_global_shutdown(void);
+
+#endif /* GRPC_CORE_LIB_IOMGR_EXEC_CTX_H */
diff --git a/src/core/lib/iomgr/executor.c b/src/core/lib/iomgr/executor.c
new file mode 100644
index 0000000000..42a9db3cbb
--- /dev/null
+++ b/src/core/lib/iomgr/executor.c
@@ -0,0 +1,143 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/executor.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd.h>
+#include "src/core/lib/iomgr/exec_ctx.h"
+
+typedef struct grpc_executor_data {
+  int busy;          /**< is the thread currently running? */
+  int shutting_down; /**< has \a grpc_shutdown() been invoked? */
+  int pending_join;  /**< has the thread finished but not been joined? */
+  grpc_closure_list closures; /**< collection of pending work */
+  gpr_thd_id tid; /**< thread id of the thread, only valid if \a busy or \a
+                     pending_join are true */
+  gpr_thd_options options;
+  gpr_mu mu;
+} grpc_executor;
+
+static grpc_executor g_executor;
+
+void grpc_executor_init() {
+  memset(&g_executor, 0, sizeof(grpc_executor));
+  gpr_mu_init(&g_executor.mu);
+  g_executor.options = gpr_thd_options_default();
+  gpr_thd_options_set_joinable(&g_executor.options);
+}
+
+/* thread body */
+static void closure_exec_thread_func(void *ignored) {
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  while (1) {
+    gpr_mu_lock(&g_executor.mu);
+    if (g_executor.shutting_down != 0) {
+      gpr_mu_unlock(&g_executor.mu);
+      break;
+    }
+    if (grpc_closure_list_empty(g_executor.closures)) {
+      /* no more work, time to die */
+      GPR_ASSERT(g_executor.busy == 1);
+      g_executor.busy = 0;
+      gpr_mu_unlock(&g_executor.mu);
+      break;
+    } else {
+      grpc_exec_ctx_enqueue_list(&exec_ctx, &g_executor.closures, NULL);
+    }
+    gpr_mu_unlock(&g_executor.mu);
+    grpc_exec_ctx_flush(&exec_ctx);
+  }
+  grpc_exec_ctx_finish(&exec_ctx);
+}
+
+/* Spawn the thread if new work has arrived a no thread is up */
+static void maybe_spawn_locked() {
+  if (grpc_closure_list_empty(g_executor.closures) == 1) {
+    return;
+  }
+  if (g_executor.shutting_down == 1) {
+    return;
+  }
+
+  if (g_executor.busy != 0) {
+    /* Thread still working. New work will be picked up by already running
+     * thread. Not spawning anything. */
+    return;
+  } else if (g_executor.pending_join != 0) {
+    /* Pickup the remains of the previous incarnations of the thread. */
+    gpr_thd_join(g_executor.tid);
+    g_executor.pending_join = 0;
+  }
+
+  /* All previous instances of the thread should have been joined at this point.
+   * Spawn time! */
+  g_executor.busy = 1;
+  gpr_thd_new(&g_executor.tid, closure_exec_thread_func, NULL,
+              &g_executor.options);
+  g_executor.pending_join = 1;
+}
+
+void grpc_executor_enqueue(grpc_closure *closure, bool success) {
+  gpr_mu_lock(&g_executor.mu);
+  if (g_executor.shutting_down == 0) {
+    grpc_closure_list_add(&g_executor.closures, closure, success);
+    maybe_spawn_locked();
+  }
+  gpr_mu_unlock(&g_executor.mu);
+}
+
+void grpc_executor_shutdown() {
+  int pending_join;
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+
+  gpr_mu_lock(&g_executor.mu);
+  pending_join = g_executor.pending_join;
+  g_executor.shutting_down = 1;
+  gpr_mu_unlock(&g_executor.mu);
+  /* we can release the lock at this point despite the access to the closure
+   * list below because we aren't accepting new work */
+
+  /* Execute pending callbacks, some may be performing cleanups */
+  grpc_exec_ctx_enqueue_list(&exec_ctx, &g_executor.closures, NULL);
+  grpc_exec_ctx_finish(&exec_ctx);
+  GPR_ASSERT(grpc_closure_list_empty(g_executor.closures));
+  if (pending_join) {
+    gpr_thd_join(g_executor.tid);
+  }
+  gpr_mu_destroy(&g_executor.mu);
+}
diff --git a/src/core/lib/iomgr/executor.h b/src/core/lib/iomgr/executor.h
new file mode 100644
index 0000000000..f1871416a0
--- /dev/null
+++ b/src/core/lib/iomgr/executor.h
@@ -0,0 +1,53 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_EXECUTOR_H
+#define GRPC_CORE_LIB_IOMGR_EXECUTOR_H
+
+#include "src/core/lib/iomgr/closure.h"
+
+/** Initialize the global executor.
+ *
+ * This mechanism is meant to outsource work (grpc_closure instances) to a
+ * thread, for those cases where blocking isn't an option but there isn't a
+ * non-blocking solution available. */
+void grpc_executor_init();
+
+/** Enqueue \a closure for its eventual execution of \a f(arg) on a separate
+ * thread */
+void grpc_executor_enqueue(grpc_closure *closure, bool success);
+
+/** Shutdown the executor, running all pending work as part of the call */
+void grpc_executor_shutdown();
+
+#endif /* GRPC_CORE_LIB_IOMGR_EXECUTOR_H */
diff --git a/src/core/lib/iomgr/iocp_windows.c b/src/core/lib/iomgr/iocp_windows.c
new file mode 100644
index 0000000000..682a32c0da
--- /dev/null
+++ b/src/core/lib/iomgr/iocp_windows.c
@@ -0,0 +1,208 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include <winsock2.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/log_win32.h>
+#include <grpc/support/thd.h>
+
+#include "src/core/lib/iomgr/iocp_windows.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+#include "src/core/lib/iomgr/timer.h"
+
+static ULONG g_iocp_kick_token;
+static OVERLAPPED g_iocp_custom_overlap;
+
+static gpr_atm g_custom_events = 0;
+
+static HANDLE g_iocp;
+
+static DWORD deadline_to_millis_timeout(gpr_timespec deadline,
+                                        gpr_timespec now) {
+  gpr_timespec timeout;
+  static const int64_t max_spin_polling_us = 10;
+  if (gpr_time_cmp(deadline, gpr_inf_future(deadline.clock_type)) == 0) {
+    return INFINITE;
+  }
+  if (gpr_time_cmp(deadline, gpr_time_add(now, gpr_time_from_micros(
+                                                   max_spin_polling_us,
+                                                   GPR_TIMESPAN))) <= 0) {
+    return 0;
+  }
+  timeout = gpr_time_sub(deadline, now);
+  return (DWORD)gpr_time_to_millis(gpr_time_add(
+      timeout, gpr_time_from_nanos(GPR_NS_PER_MS - 1, GPR_TIMESPAN)));
+}
+
+grpc_iocp_work_status grpc_iocp_work(grpc_exec_ctx *exec_ctx,
+                                     gpr_timespec deadline) {
+  BOOL success;
+  DWORD bytes = 0;
+  DWORD flags = 0;
+  ULONG_PTR completion_key;
+  LPOVERLAPPED overlapped;
+  grpc_winsocket *socket;
+  grpc_winsocket_callback_info *info;
+  grpc_closure *closure = NULL;
+  success = GetQueuedCompletionStatus(
+      g_iocp, &bytes, &completion_key, &overlapped,
+      deadline_to_millis_timeout(deadline, gpr_now(deadline.clock_type)));
+  if (success == 0 && overlapped == NULL) {
+    return GRPC_IOCP_WORK_TIMEOUT;
+  }
+  GPR_ASSERT(completion_key && overlapped);
+  if (overlapped == &g_iocp_custom_overlap) {
+    gpr_atm_full_fetch_add(&g_custom_events, -1);
+    if (completion_key == (ULONG_PTR)&g_iocp_kick_token) {
+      /* We were awoken from a kick. */
+      return GRPC_IOCP_WORK_KICK;
+    }
+    gpr_log(GPR_ERROR, "Unknown custom completion key.");
+    abort();
+  }
+
+  socket = (grpc_winsocket *)completion_key;
+  if (overlapped == &socket->write_info.overlapped) {
+    info = &socket->write_info;
+  } else if (overlapped == &socket->read_info.overlapped) {
+    info = &socket->read_info;
+  } else {
+    gpr_log(GPR_ERROR, "Unknown IOCP operation");
+    abort();
+  }
+  success = WSAGetOverlappedResult(socket->socket, &info->overlapped, &bytes,
+                                   FALSE, &flags);
+  info->bytes_transfered = bytes;
+  info->wsa_error = success ? 0 : WSAGetLastError();
+  GPR_ASSERT(overlapped == &info->overlapped);
+  GPR_ASSERT(!info->has_pending_iocp);
+  gpr_mu_lock(&socket->state_mu);
+  if (info->closure) {
+    closure = info->closure;
+    info->closure = NULL;
+  } else {
+    info->has_pending_iocp = 1;
+  }
+  gpr_mu_unlock(&socket->state_mu);
+  grpc_exec_ctx_enqueue(exec_ctx, closure, true, NULL);
+  return GRPC_IOCP_WORK_WORK;
+}
+
+void grpc_iocp_init(void) {
+  g_iocp =
+      CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, (ULONG_PTR)NULL, 0);
+  GPR_ASSERT(g_iocp);
+}
+
+void grpc_iocp_kick(void) {
+  BOOL success;
+
+  gpr_atm_full_fetch_add(&g_custom_events, 1);
+  success = PostQueuedCompletionStatus(g_iocp, 0, (ULONG_PTR)&g_iocp_kick_token,
+                                       &g_iocp_custom_overlap);
+  GPR_ASSERT(success);
+}
+
+void grpc_iocp_flush(void) {
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_iocp_work_status work_status;
+
+  do {
+    work_status = grpc_iocp_work(&exec_ctx, gpr_inf_past(GPR_CLOCK_MONOTONIC));
+  } while (work_status == GRPC_IOCP_WORK_KICK ||
+           grpc_exec_ctx_flush(&exec_ctx));
+}
+
+void grpc_iocp_shutdown(void) {
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  while (gpr_atm_acq_load(&g_custom_events)) {
+    grpc_iocp_work(&exec_ctx, gpr_inf_future(GPR_CLOCK_MONOTONIC));
+    grpc_exec_ctx_flush(&exec_ctx);
+  }
+  grpc_exec_ctx_finish(&exec_ctx);
+  GPR_ASSERT(CloseHandle(g_iocp));
+}
+
+void grpc_iocp_add_socket(grpc_winsocket *socket) {
+  HANDLE ret;
+  if (socket->added_to_iocp) return;
+  ret = CreateIoCompletionPort((HANDLE)socket->socket, g_iocp,
+                               (uintptr_t)socket, 0);
+  if (!ret) {
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    gpr_log(GPR_ERROR, "Unable to add socket to iocp: %s", utf8_message);
+    gpr_free(utf8_message);
+    __debugbreak();
+    abort();
+  }
+  socket->added_to_iocp = 1;
+  GPR_ASSERT(ret == g_iocp);
+}
+
+/* Calling notify_on_read or write means either of two things:
+   -) The IOCP already completed in the background, and we need to call
+   the callback now.
+   -) The IOCP hasn't completed yet, and we're queuing it for later. */
+static void socket_notify_on_iocp(grpc_exec_ctx *exec_ctx,
+                                  grpc_winsocket *socket, grpc_closure *closure,
+                                  grpc_winsocket_callback_info *info) {
+  GPR_ASSERT(info->closure == NULL);
+  gpr_mu_lock(&socket->state_mu);
+  if (info->has_pending_iocp) {
+    info->has_pending_iocp = 0;
+    grpc_exec_ctx_enqueue(exec_ctx, closure, true, NULL);
+  } else {
+    info->closure = closure;
+  }
+  gpr_mu_unlock(&socket->state_mu);
+}
+
+void grpc_socket_notify_on_write(grpc_exec_ctx *exec_ctx,
+                                 grpc_winsocket *socket,
+                                 grpc_closure *closure) {
+  socket_notify_on_iocp(exec_ctx, socket, closure, &socket->write_info);
+}
+
+void grpc_socket_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_winsocket *socket,
+                                grpc_closure *closure) {
+  socket_notify_on_iocp(exec_ctx, socket, closure, &socket->read_info);
+}
+
+#endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/iocp_windows.h b/src/core/lib/iomgr/iocp_windows.h
new file mode 100644
index 0000000000..856c837fb4
--- /dev/null
+++ b/src/core/lib/iomgr/iocp_windows.h
@@ -0,0 +1,63 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_IOCP_WINDOWS_H
+#define GRPC_CORE_LIB_IOMGR_IOCP_WINDOWS_H
+
+#include <grpc/support/sync.h>
+
+#include "src/core/lib/iomgr/socket_windows.h"
+
+typedef enum {
+  GRPC_IOCP_WORK_WORK,
+  GRPC_IOCP_WORK_TIMEOUT,
+  GRPC_IOCP_WORK_KICK
+} grpc_iocp_work_status;
+
+grpc_iocp_work_status grpc_iocp_work(grpc_exec_ctx *exec_ctx,
+                                     gpr_timespec deadline);
+void grpc_iocp_init(void);
+void grpc_iocp_kick(void);
+void grpc_iocp_flush(void);
+void grpc_iocp_shutdown(void);
+void grpc_iocp_add_socket(grpc_winsocket *);
+
+void grpc_socket_notify_on_write(grpc_exec_ctx *exec_ctx,
+                                 grpc_winsocket *winsocket,
+                                 grpc_closure *closure);
+
+void grpc_socket_notify_on_read(grpc_exec_ctx *exec_ctx,
+                                grpc_winsocket *winsocket,
+                                grpc_closure *closure);
+
+#endif /* GRPC_CORE_LIB_IOMGR_IOCP_WINDOWS_H */
diff --git a/src/core/lib/iomgr/iomgr.c b/src/core/lib/iomgr/iomgr.c
new file mode 100644
index 0000000000..e74a7c29df
--- /dev/null
+++ b/src/core/lib/iomgr/iomgr.c
@@ -0,0 +1,173 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/iomgr.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd.h>
+#include <grpc/support/useful.h>
+
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/timer.h"
+#include "src/core/lib/support/env.h"
+#include "src/core/lib/support/string.h"
+
+static gpr_mu g_mu;
+static gpr_cv g_rcv;
+static int g_shutdown;
+static grpc_iomgr_object g_root_object;
+
+void grpc_iomgr_init(void) {
+  g_shutdown = 0;
+  gpr_mu_init(&g_mu);
+  gpr_cv_init(&g_rcv);
+  grpc_exec_ctx_global_init();
+  grpc_timer_list_init(gpr_now(GPR_CLOCK_MONOTONIC));
+  g_root_object.next = g_root_object.prev = &g_root_object;
+  g_root_object.name = "root";
+  grpc_iomgr_platform_init();
+}
+
+static size_t count_objects(void) {
+  grpc_iomgr_object *obj;
+  size_t n = 0;
+  for (obj = g_root_object.next; obj != &g_root_object; obj = obj->next) {
+    n++;
+  }
+  return n;
+}
+
+static void dump_objects(const char *kind) {
+  grpc_iomgr_object *obj;
+  for (obj = g_root_object.next; obj != &g_root_object; obj = obj->next) {
+    gpr_log(GPR_DEBUG, "%s OBJECT: %s %p", kind, obj->name, obj);
+  }
+}
+
+void grpc_iomgr_shutdown(void) {
+  gpr_timespec shutdown_deadline = gpr_time_add(
+      gpr_now(GPR_CLOCK_REALTIME), gpr_time_from_seconds(10, GPR_TIMESPAN));
+  gpr_timespec last_warning_time = gpr_now(GPR_CLOCK_REALTIME);
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+
+  grpc_iomgr_platform_flush();
+
+  gpr_mu_lock(&g_mu);
+  g_shutdown = 1;
+  while (g_root_object.next != &g_root_object) {
+    if (gpr_time_cmp(
+            gpr_time_sub(gpr_now(GPR_CLOCK_REALTIME), last_warning_time),
+            gpr_time_from_seconds(1, GPR_TIMESPAN)) >= 0) {
+      if (g_root_object.next != &g_root_object) {
+        gpr_log(GPR_DEBUG, "Waiting for %d iomgr objects to be destroyed",
+                count_objects());
+      }
+      last_warning_time = gpr_now(GPR_CLOCK_REALTIME);
+    }
+    if (grpc_timer_check(&exec_ctx, gpr_inf_future(GPR_CLOCK_MONOTONIC),
+                         NULL)) {
+      gpr_mu_unlock(&g_mu);
+      grpc_exec_ctx_flush(&exec_ctx);
+      gpr_mu_lock(&g_mu);
+      continue;
+    }
+    if (g_root_object.next != &g_root_object) {
+      gpr_timespec short_deadline = gpr_time_add(
+          gpr_now(GPR_CLOCK_REALTIME), gpr_time_from_millis(100, GPR_TIMESPAN));
+      if (gpr_cv_wait(&g_rcv, &g_mu, short_deadline)) {
+        if (gpr_time_cmp(gpr_now(GPR_CLOCK_REALTIME), shutdown_deadline) > 0) {
+          if (g_root_object.next != &g_root_object) {
+            gpr_log(GPR_DEBUG,
+                    "Failed to free %d iomgr objects before shutdown deadline: "
+                    "memory leaks are likely",
+                    count_objects());
+            dump_objects("LEAKED");
+            if (grpc_iomgr_abort_on_leaks()) {
+              abort();
+            }
+          }
+          break;
+        }
+      }
+    }
+  }
+  gpr_mu_unlock(&g_mu);
+
+  grpc_timer_list_shutdown(&exec_ctx);
+  grpc_exec_ctx_finish(&exec_ctx);
+
+  /* ensure all threads have left g_mu */
+  gpr_mu_lock(&g_mu);
+  gpr_mu_unlock(&g_mu);
+
+  grpc_iomgr_platform_shutdown();
+  grpc_exec_ctx_global_shutdown();
+  gpr_mu_destroy(&g_mu);
+  gpr_cv_destroy(&g_rcv);
+}
+
+void grpc_iomgr_register_object(grpc_iomgr_object *obj, const char *name) {
+  obj->name = gpr_strdup(name);
+  gpr_mu_lock(&g_mu);
+  obj->next = &g_root_object;
+  obj->prev = g_root_object.prev;
+  obj->next->prev = obj->prev->next = obj;
+  gpr_mu_unlock(&g_mu);
+}
+
+void grpc_iomgr_unregister_object(grpc_iomgr_object *obj) {
+  gpr_mu_lock(&g_mu);
+  obj->next->prev = obj->prev;
+  obj->prev->next = obj->next;
+  gpr_cv_signal(&g_rcv);
+  gpr_mu_unlock(&g_mu);
+  gpr_free(obj->name);
+}
+
+bool grpc_iomgr_abort_on_leaks(void) {
+  char *env = gpr_getenv("GRPC_ABORT_ON_LEAKS");
+  if (env == NULL) return false;
+  static const char *truthy[] = {"yes",  "Yes",  "YES", "true",
+                                 "True", "TRUE", "1"};
+  for (size_t i = 0; i < GPR_ARRAY_SIZE(truthy); i++) {
+    if (0 == strcmp(env, truthy[i])) return true;
+  }
+  return false;
+}
diff --git a/src/core/lib/iomgr/iomgr.h b/src/core/lib/iomgr/iomgr.h
new file mode 100644
index 0000000000..babf0a85b7
--- /dev/null
+++ b/src/core/lib/iomgr/iomgr.h
@@ -0,0 +1,43 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_IOMGR_H
+#define GRPC_CORE_LIB_IOMGR_IOMGR_H
+
+/** Initializes the iomgr. */
+void grpc_iomgr_init(void);
+
+/** Signals the intention to shutdown the iomgr. */
+void grpc_iomgr_shutdown(void);
+
+#endif /* GRPC_CORE_LIB_IOMGR_IOMGR_H */
diff --git a/src/core/lib/iomgr/iomgr_internal.h b/src/core/lib/iomgr/iomgr_internal.h
new file mode 100644
index 0000000000..404f402c9a
--- /dev/null
+++ b/src/core/lib/iomgr/iomgr_internal.h
@@ -0,0 +1,58 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_IOMGR_INTERNAL_H
+#define GRPC_CORE_LIB_IOMGR_IOMGR_INTERNAL_H
+
+#include <stdbool.h>
+
+#include "src/core/lib/iomgr/iomgr.h"
+
+typedef struct grpc_iomgr_object {
+  char *name;
+  struct grpc_iomgr_object *next;
+  struct grpc_iomgr_object *prev;
+} grpc_iomgr_object;
+
+void grpc_iomgr_register_object(grpc_iomgr_object *obj, const char *name);
+void grpc_iomgr_unregister_object(grpc_iomgr_object *obj);
+
+void grpc_iomgr_platform_init(void);
+/** flush any globally queued work from iomgr */
+void grpc_iomgr_platform_flush(void);
+/** tear down all platform specific global iomgr structures */
+void grpc_iomgr_platform_shutdown(void);
+
+bool grpc_iomgr_abort_on_leaks(void);
+
+#endif /* GRPC_CORE_LIB_IOMGR_IOMGR_INTERNAL_H */
diff --git a/src/core/lib/iomgr/iomgr_posix.c b/src/core/lib/iomgr/iomgr_posix.c
new file mode 100644
index 0000000000..641caa1dc1
--- /dev/null
+++ b/src/core/lib/iomgr/iomgr_posix.c
@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/iomgr/ev_posix.h"
+#include "src/core/lib/iomgr/iomgr_posix.h"
+#include "src/core/lib/iomgr/tcp_posix.h"
+
+void grpc_iomgr_platform_init(void) {
+  grpc_event_engine_init();
+  grpc_register_tracer("tcp", &grpc_tcp_trace);
+}
+
+void grpc_iomgr_platform_flush(void) {}
+
+void grpc_iomgr_platform_shutdown(void) { grpc_event_engine_shutdown(); }
+
+#endif /* GRPC_POSIX_SOCKET */
diff --git a/src/core/lib/iomgr/iomgr_posix.h b/src/core/lib/iomgr/iomgr_posix.h
new file mode 100644
index 0000000000..6a8996e403
--- /dev/null
+++ b/src/core/lib/iomgr/iomgr_posix.h
@@ -0,0 +1,39 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_IOMGR_POSIX_H
+#define GRPC_CORE_LIB_IOMGR_IOMGR_POSIX_H
+
+#include "src/core/lib/iomgr/iomgr_internal.h"
+
+#endif /* GRPC_CORE_LIB_IOMGR_IOMGR_POSIX_H */
diff --git a/src/core/lib/iomgr/iomgr_windows.c b/src/core/lib/iomgr/iomgr_windows.c
new file mode 100644
index 0000000000..af7e616394
--- /dev/null
+++ b/src/core/lib/iomgr/iomgr_windows.c
@@ -0,0 +1,73 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include "src/core/lib/iomgr/sockaddr_win32.h"
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/iomgr/iocp_windows.h"
+#include "src/core/lib/iomgr/iomgr.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+
+/* Windows' io manager is going to be fully designed using IO completion
+   ports. All of what we're doing here is basically make sure that
+   Windows sockets are initialized in and out. */
+
+static void winsock_init(void) {
+  WSADATA wsaData;
+  int status = WSAStartup(MAKEWORD(2, 0), &wsaData);
+  GPR_ASSERT(status == 0);
+}
+
+static void winsock_shutdown(void) {
+  int status = WSACleanup();
+  GPR_ASSERT(status == 0);
+}
+
+void grpc_iomgr_platform_init(void) {
+  winsock_init();
+  grpc_iocp_init();
+}
+
+void grpc_iomgr_platform_flush(void) { grpc_iocp_flush(); }
+
+void grpc_iomgr_platform_shutdown(void) {
+  grpc_iocp_shutdown();
+  winsock_shutdown();
+}
+
+#endif /* GRPC_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/pollset.h b/src/core/lib/iomgr/pollset.h
new file mode 100644
index 0000000000..6156124862
--- /dev/null
+++ b/src/core/lib/iomgr/pollset.h
@@ -0,0 +1,94 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_POLLSET_H
+#define GRPC_CORE_LIB_IOMGR_POLLSET_H
+
+#include <grpc/support/port_platform.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/time.h>
+
+#include "src/core/lib/iomgr/exec_ctx.h"
+
+#define GRPC_POLLSET_KICK_BROADCAST ((grpc_pollset_worker *)1)
+
+/* A grpc_pollset is a set of file descriptors that a higher level item is
+   interested in. For example:
+    - a server will typically keep a pollset containing all connected channels,
+      so that it can find new calls to service
+    - a completion queue might keep a pollset with an entry for each transport
+      that is servicing a call that it's tracking */
+
+typedef struct grpc_pollset grpc_pollset;
+typedef struct grpc_pollset_worker grpc_pollset_worker;
+
+size_t grpc_pollset_size(void);
+void grpc_pollset_init(grpc_pollset *pollset, gpr_mu **mu);
+/* Begin shutting down the pollset, and call closure when done.
+ * pollset's mutex must be held */
+void grpc_pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           grpc_closure *closure);
+/** Reset the pollset to its initial state (perhaps with some cached objects);
+ *  must have been previously shutdown */
+void grpc_pollset_reset(grpc_pollset *pollset);
+void grpc_pollset_destroy(grpc_pollset *pollset);
+
+/* Do some work on a pollset.
+   May involve invoking asynchronous callbacks, or actually polling file
+   descriptors.
+   Requires pollset's mutex locked.
+   May unlock its mutex during its execution.
+
+   worker is a (platform-specific) handle that can be used to wake up
+   from grpc_pollset_work before any events are received and before the timeout
+   has expired. It is both initialized and destroyed by grpc_pollset_work.
+   Initialization of worker is guaranteed to occur BEFORE the
+   pollset's mutex is released for the first time by grpc_pollset_work
+   and it is guaranteed that it will not be released by grpc_pollset_work
+   AFTER worker has been destroyed.
+
+   Tries not to block past deadline.
+   May call grpc_closure_list_run on grpc_closure_list, without holding the
+   pollset
+   lock */
+void grpc_pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                       grpc_pollset_worker **worker, gpr_timespec now,
+                       gpr_timespec deadline);
+
+/* Break one polling thread out of polling work for this pollset.
+   If specific_worker is GRPC_POLLSET_KICK_BROADCAST, kick ALL the workers.
+   Otherwise, if specific_worker is non-NULL, then kick that worker. */
+void grpc_pollset_kick(grpc_pollset *pollset,
+                       grpc_pollset_worker *specific_worker);
+
+#endif /* GRPC_CORE_LIB_IOMGR_POLLSET_H */
diff --git a/src/core/lib/iomgr/pollset_set.h b/src/core/lib/iomgr/pollset_set.h
new file mode 100644
index 0000000000..fb29d692d7
--- /dev/null
+++ b/src/core/lib/iomgr/pollset_set.h
@@ -0,0 +1,61 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_POLLSET_SET_H
+#define GRPC_CORE_LIB_IOMGR_POLLSET_SET_H
+
+#include "src/core/lib/iomgr/pollset.h"
+
+/* A grpc_pollset_set is a set of pollsets that are interested in an
+   action. Adding a pollset to a pollset_set automatically adds any
+   fd's (etc) that have been registered with the set_set to that pollset.
+   Registering fd's automatically adds them to all current pollsets. */
+
+typedef struct grpc_pollset_set grpc_pollset_set;
+
+grpc_pollset_set *grpc_pollset_set_create(void);
+void grpc_pollset_set_destroy(grpc_pollset_set *pollset_set);
+void grpc_pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset);
+void grpc_pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset);
+void grpc_pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item);
+void grpc_pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item);
+
+#endif /* GRPC_CORE_LIB_IOMGR_POLLSET_SET_H */
diff --git a/src/core/lib/iomgr/pollset_set_windows.c b/src/core/lib/iomgr/pollset_set_windows.c
new file mode 100644
index 0000000000..0b14e446ae
--- /dev/null
+++ b/src/core/lib/iomgr/pollset_set_windows.c
@@ -0,0 +1,60 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include "src/core/lib/iomgr/pollset_set_windows.h"
+
+grpc_pollset_set* grpc_pollset_set_create(pollset_set) { return NULL; }
+
+void grpc_pollset_set_destroy(grpc_pollset_set* pollset_set) {}
+
+void grpc_pollset_set_add_pollset(grpc_exec_ctx* exec_ctx,
+                                  grpc_pollset_set* pollset_set,
+                                  grpc_pollset* pollset) {}
+
+void grpc_pollset_set_del_pollset(grpc_exec_ctx* exec_ctx,
+                                  grpc_pollset_set* pollset_set,
+                                  grpc_pollset* pollset) {}
+
+void grpc_pollset_set_add_pollset_set(grpc_exec_ctx* exec_ctx,
+                                      grpc_pollset_set* bag,
+                                      grpc_pollset_set* item) {}
+
+void grpc_pollset_set_del_pollset_set(grpc_exec_ctx* exec_ctx,
+                                      grpc_pollset_set* bag,
+                                      grpc_pollset_set* item) {}
+
+#endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/pollset_set_windows.h b/src/core/lib/iomgr/pollset_set_windows.h
new file mode 100644
index 0000000000..7c2cea23de
--- /dev/null
+++ b/src/core/lib/iomgr/pollset_set_windows.h
@@ -0,0 +1,39 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_POLLSET_SET_WINDOWS_H
+#define GRPC_CORE_LIB_IOMGR_POLLSET_SET_WINDOWS_H
+
+#include "src/core/lib/iomgr/pollset_set.h"
+
+#endif /* GRPC_CORE_LIB_IOMGR_POLLSET_SET_WINDOWS_H */
diff --git a/src/core/lib/iomgr/pollset_windows.c b/src/core/lib/iomgr/pollset_windows.c
new file mode 100644
index 0000000000..6b339127a8
--- /dev/null
+++ b/src/core/lib/iomgr/pollset_windows.c
@@ -0,0 +1,240 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include <grpc/support/log.h>
+#include <grpc/support/thd.h>
+
+#include "src/core/lib/iomgr/iocp_windows.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/pollset.h"
+#include "src/core/lib/iomgr/pollset_windows.h"
+
+gpr_mu grpc_polling_mu;
+static grpc_pollset_worker *g_active_poller;
+static grpc_pollset_worker g_global_root_worker;
+
+void grpc_pollset_global_init() {
+  gpr_mu_init(&grpc_polling_mu);
+  g_active_poller = NULL;
+  g_global_root_worker.links[GRPC_POLLSET_WORKER_LINK_GLOBAL].next =
+      g_global_root_worker.links[GRPC_POLLSET_WORKER_LINK_GLOBAL].prev =
+          &g_global_root_worker;
+}
+
+void grpc_pollset_global_shutdown() { gpr_mu_destroy(&grpc_polling_mu); }
+
+static void remove_worker(grpc_pollset_worker *worker,
+                          grpc_pollset_worker_link_type type) {
+  worker->links[type].prev->links[type].next = worker->links[type].next;
+  worker->links[type].next->links[type].prev = worker->links[type].prev;
+  worker->links[type].next = worker->links[type].prev = worker;
+}
+
+static int has_workers(grpc_pollset_worker *root,
+                       grpc_pollset_worker_link_type type) {
+  return root->links[type].next != root;
+}
+
+static grpc_pollset_worker *pop_front_worker(
+    grpc_pollset_worker *root, grpc_pollset_worker_link_type type) {
+  if (has_workers(root, type)) {
+    grpc_pollset_worker *w = root->links[type].next;
+    remove_worker(w, type);
+    return w;
+  } else {
+    return NULL;
+  }
+}
+
+static void push_front_worker(grpc_pollset_worker *root,
+                              grpc_pollset_worker_link_type type,
+                              grpc_pollset_worker *worker) {
+  worker->links[type].prev = root;
+  worker->links[type].next = worker->links[type].prev->links[type].next;
+  worker->links[type].prev->links[type].next =
+      worker->links[type].next->links[type].prev = worker;
+}
+
+size_t grpc_pollset_size(void) { return sizeof(grpc_pollset); }
+
+/* There isn't really any such thing as a pollset under Windows, due to the
+   nature of the IO completion ports. We're still going to provide a minimal
+   set of features for the sake of the rest of grpc. But grpc_pollset_work
+   won't actually do any polling, and return as quickly as possible. */
+
+void grpc_pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
+  *mu = &grpc_polling_mu;
+  memset(pollset, 0, sizeof(*pollset));
+  pollset->root_worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].next =
+      pollset->root_worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].prev =
+          &pollset->root_worker;
+}
+
+void grpc_pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           grpc_closure *closure) {
+  pollset->shutting_down = 1;
+  grpc_pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
+  if (!pollset->is_iocp_worker) {
+    grpc_exec_ctx_enqueue(exec_ctx, closure, true, NULL);
+  } else {
+    pollset->on_shutdown = closure;
+  }
+}
+
+void grpc_pollset_destroy(grpc_pollset *pollset) {}
+
+void grpc_pollset_reset(grpc_pollset *pollset) {
+  GPR_ASSERT(pollset->shutting_down);
+  GPR_ASSERT(
+      !has_workers(&pollset->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET));
+  pollset->shutting_down = 0;
+  pollset->is_iocp_worker = 0;
+  pollset->kicked_without_pollers = 0;
+  pollset->on_shutdown = NULL;
+}
+
+void grpc_pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                       grpc_pollset_worker **worker_hdl, gpr_timespec now,
+                       gpr_timespec deadline) {
+  grpc_pollset_worker worker;
+  *worker_hdl = &worker;
+
+  int added_worker = 0;
+  worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].next =
+      worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].prev =
+          worker.links[GRPC_POLLSET_WORKER_LINK_GLOBAL].next =
+              worker.links[GRPC_POLLSET_WORKER_LINK_GLOBAL].prev = NULL;
+  worker.kicked = 0;
+  worker.pollset = pollset;
+  gpr_cv_init(&worker.cv);
+  if (!pollset->kicked_without_pollers && !pollset->shutting_down) {
+    if (g_active_poller == NULL) {
+      grpc_pollset_worker *next_worker;
+      /* become poller */
+      pollset->is_iocp_worker = 1;
+      g_active_poller = &worker;
+      gpr_mu_unlock(&grpc_polling_mu);
+      grpc_iocp_work(exec_ctx, deadline);
+      grpc_exec_ctx_flush(exec_ctx);
+      gpr_mu_lock(&grpc_polling_mu);
+      pollset->is_iocp_worker = 0;
+      g_active_poller = NULL;
+      /* try to get a worker from this pollsets worker list */
+      next_worker = pop_front_worker(&pollset->root_worker,
+                                     GRPC_POLLSET_WORKER_LINK_POLLSET);
+      if (next_worker == NULL) {
+        /* try to get a worker from the global list */
+        next_worker = pop_front_worker(&g_global_root_worker,
+                                       GRPC_POLLSET_WORKER_LINK_GLOBAL);
+      }
+      if (next_worker != NULL) {
+        next_worker->kicked = 1;
+        gpr_cv_signal(&next_worker->cv);
+      }
+
+      if (pollset->shutting_down && pollset->on_shutdown != NULL) {
+        grpc_exec_ctx_enqueue(exec_ctx, pollset->on_shutdown, true, NULL);
+        pollset->on_shutdown = NULL;
+      }
+      goto done;
+    }
+    push_front_worker(&g_global_root_worker, GRPC_POLLSET_WORKER_LINK_GLOBAL,
+                      &worker);
+    push_front_worker(&pollset->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET,
+                      &worker);
+    added_worker = 1;
+    while (!worker.kicked) {
+      if (gpr_cv_wait(&worker.cv, &grpc_polling_mu, deadline)) {
+        break;
+      }
+    }
+  } else {
+    pollset->kicked_without_pollers = 0;
+  }
+done:
+  if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
+    gpr_mu_unlock(&grpc_polling_mu);
+    grpc_exec_ctx_flush(exec_ctx);
+    gpr_mu_lock(&grpc_polling_mu);
+  }
+  if (added_worker) {
+    remove_worker(&worker, GRPC_POLLSET_WORKER_LINK_GLOBAL);
+    remove_worker(&worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
+  }
+  gpr_cv_destroy(&worker.cv);
+  *worker_hdl = NULL;
+}
+
+void grpc_pollset_kick(grpc_pollset *p, grpc_pollset_worker *specific_worker) {
+  if (specific_worker != NULL) {
+    if (specific_worker == GRPC_POLLSET_KICK_BROADCAST) {
+      for (specific_worker =
+               p->root_worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].next;
+           specific_worker != &p->root_worker;
+           specific_worker =
+               specific_worker->links[GRPC_POLLSET_WORKER_LINK_POLLSET].next) {
+        specific_worker->kicked = 1;
+        gpr_cv_signal(&specific_worker->cv);
+      }
+      p->kicked_without_pollers = 1;
+      if (p->is_iocp_worker) {
+        grpc_iocp_kick();
+      }
+    } else {
+      if (p->is_iocp_worker && g_active_poller == specific_worker) {
+        grpc_iocp_kick();
+      } else {
+        specific_worker->kicked = 1;
+        gpr_cv_signal(&specific_worker->cv);
+      }
+    }
+  } else {
+    specific_worker =
+        pop_front_worker(&p->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
+    if (specific_worker != NULL) {
+      grpc_pollset_kick(p, specific_worker);
+    } else if (p->is_iocp_worker) {
+      grpc_iocp_kick();
+    } else {
+      p->kicked_without_pollers = 1;
+    }
+  }
+}
+
+void grpc_kick_poller(void) { grpc_iocp_kick(); }
+
+#endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/pollset_windows.h b/src/core/lib/iomgr/pollset_windows.h
new file mode 100644
index 0000000000..fa9553ffea
--- /dev/null
+++ b/src/core/lib/iomgr/pollset_windows.h
@@ -0,0 +1,75 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_POLLSET_WINDOWS_H
+#define GRPC_CORE_LIB_IOMGR_POLLSET_WINDOWS_H
+
+#include <grpc/support/sync.h>
+
+#include "src/core/lib/iomgr/socket_windows.h"
+
+/* There isn't really any such thing as a pollset under Windows, due to the
+   nature of the IO completion ports. A Windows "pollset" is merely a mutex
+   used to synchronize with the IOCP, and workers are condition variables
+   used to block threads until work is ready. */
+
+typedef enum {
+  GRPC_POLLSET_WORKER_LINK_POLLSET = 0,
+  GRPC_POLLSET_WORKER_LINK_GLOBAL,
+  GRPC_POLLSET_WORKER_LINK_TYPES
+} grpc_pollset_worker_link_type;
+
+typedef struct grpc_pollset_worker_link {
+  struct grpc_pollset_worker *next;
+  struct grpc_pollset_worker *prev;
+} grpc_pollset_worker_link;
+
+struct grpc_pollset;
+typedef struct grpc_pollset grpc_pollset;
+
+typedef struct grpc_pollset_worker {
+  gpr_cv cv;
+  int kicked;
+  struct grpc_pollset *pollset;
+  grpc_pollset_worker_link links[GRPC_POLLSET_WORKER_LINK_TYPES];
+} grpc_pollset_worker;
+
+struct grpc_pollset {
+  int shutting_down;
+  int kicked_without_pollers;
+  int is_iocp_worker;
+  grpc_pollset_worker root_worker;
+  grpc_closure *on_shutdown;
+};
+
+#endif /* GRPC_CORE_LIB_IOMGR_POLLSET_WINDOWS_H */
diff --git a/src/core/lib/iomgr/resolve_address.h b/src/core/lib/iomgr/resolve_address.h
new file mode 100644
index 0000000000..f748288685
--- /dev/null
+++ b/src/core/lib/iomgr/resolve_address.h
@@ -0,0 +1,72 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_RESOLVE_ADDRESS_H
+#define GRPC_CORE_LIB_IOMGR_RESOLVE_ADDRESS_H
+
+#include <stddef.h>
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/iomgr.h"
+
+#define GRPC_MAX_SOCKADDR_SIZE 128
+
+typedef struct {
+  char addr[GRPC_MAX_SOCKADDR_SIZE];
+  size_t len;
+} grpc_resolved_address;
+
+typedef struct {
+  size_t naddrs;
+  grpc_resolved_address *addrs;
+} grpc_resolved_addresses;
+
+/* Async result callback:
+   On success: addresses is the result, and the callee must call
+   grpc_resolved_addresses_destroy when it's done with them
+   On failure: addresses is NULL */
+typedef void (*grpc_resolve_cb)(grpc_exec_ctx *exec_ctx, void *arg,
+                                grpc_resolved_addresses *addresses);
+/* Asynchronously resolve addr. Use default_port if a port isn't designated
+   in addr, otherwise use the port in addr. */
+/* TODO(ctiller): add a timeout here */
+void grpc_resolve_address(const char *addr, const char *default_port,
+                          grpc_resolve_cb cb, void *arg);
+/* Destroy resolved addresses */
+void grpc_resolved_addresses_destroy(grpc_resolved_addresses *addresses);
+
+/* Resolve addr in a blocking fashion. Returns NULL on failure. On success,
+   result must be freed with grpc_resolved_addresses_destroy. */
+extern grpc_resolved_addresses *(*grpc_blocking_resolve_address)(
+    const char *name, const char *default_port);
+
+#endif /* GRPC_CORE_LIB_IOMGR_RESOLVE_ADDRESS_H */
diff --git a/src/core/lib/iomgr/resolve_address_posix.c b/src/core/lib/iomgr/resolve_address_posix.c
new file mode 100644
index 0000000000..ebecb39c16
--- /dev/null
+++ b/src/core/lib/iomgr/resolve_address_posix.c
@@ -0,0 +1,178 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+
+#include <string.h>
+#include <sys/types.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/host_port.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/thd.h>
+#include <grpc/support/time.h>
+#include <grpc/support/useful.h>
+#include "src/core/lib/iomgr/executor.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+#include "src/core/lib/support/block_annotate.h"
+#include "src/core/lib/support/string.h"
+
+typedef struct {
+  char *name;
+  char *default_port;
+  grpc_resolve_cb cb;
+  grpc_closure request_closure;
+  void *arg;
+} request;
+
+static grpc_resolved_addresses *blocking_resolve_address_impl(
+    const char *name, const char *default_port) {
+  struct addrinfo hints;
+  struct addrinfo *result = NULL, *resp;
+  char *host;
+  char *port;
+  int s;
+  size_t i;
+  grpc_resolved_addresses *addrs = NULL;
+
+  if (name[0] == 'u' && name[1] == 'n' && name[2] == 'i' && name[3] == 'x' &&
+      name[4] == ':' && name[5] != 0) {
+    return grpc_resolve_unix_domain_address(name + 5);
+  }
+
+  /* parse name, splitting it into host and port parts */
+  gpr_split_host_port(name, &host, &port);
+  if (host == NULL) {
+    gpr_log(GPR_ERROR, "unparseable host:port: '%s'", name);
+    goto done;
+  }
+  if (port == NULL) {
+    if (default_port == NULL) {
+      gpr_log(GPR_ERROR, "no port in name '%s'", name);
+      goto done;
+    }
+    port = gpr_strdup(default_port);
+  }
+
+  /* Call getaddrinfo */
+  memset(&hints, 0, sizeof(hints));
+  hints.ai_family = AF_UNSPEC;     /* ipv4 or ipv6 */
+  hints.ai_socktype = SOCK_STREAM; /* stream socket */
+  hints.ai_flags = AI_PASSIVE;     /* for wildcard IP address */
+
+  GRPC_SCHEDULING_START_BLOCKING_REGION;
+  s = getaddrinfo(host, port, &hints, &result);
+  GRPC_SCHEDULING_END_BLOCKING_REGION;
+
+  if (s != 0) {
+    /* Retry if well-known service name is recognized */
+    char *svc[][2] = {{"http", "80"}, {"https", "443"}};
+    for (i = 0; i < GPR_ARRAY_SIZE(svc); i++) {
+      if (strcmp(port, svc[i][0]) == 0) {
+        GRPC_SCHEDULING_START_BLOCKING_REGION;
+        s = getaddrinfo(host, svc[i][1], &hints, &result);
+        GRPC_SCHEDULING_END_BLOCKING_REGION;
+        break;
+      }
+    }
+  }
+
+  if (s != 0) {
+    gpr_log(GPR_ERROR, "getaddrinfo: %s", gai_strerror(s));
+    goto done;
+  }
+
+  /* Success path: set addrs non-NULL, fill it in */
+  addrs = gpr_malloc(sizeof(grpc_resolved_addresses));
+  addrs->naddrs = 0;
+  for (resp = result; resp != NULL; resp = resp->ai_next) {
+    addrs->naddrs++;
+  }
+  addrs->addrs = gpr_malloc(sizeof(grpc_resolved_address) * addrs->naddrs);
+  i = 0;
+  for (resp = result; resp != NULL; resp = resp->ai_next) {
+    memcpy(&addrs->addrs[i].addr, resp->ai_addr, resp->ai_addrlen);
+    addrs->addrs[i].len = resp->ai_addrlen;
+    i++;
+  }
+
+done:
+  gpr_free(host);
+  gpr_free(port);
+  if (result) {
+    freeaddrinfo(result);
+  }
+  return addrs;
+}
+
+grpc_resolved_addresses *(*grpc_blocking_resolve_address)(
+    const char *name, const char *default_port) = blocking_resolve_address_impl;
+
+/* Callback to be passed to grpc_executor to asynch-ify
+ * grpc_blocking_resolve_address */
+static void do_request_thread(grpc_exec_ctx *exec_ctx, void *rp, bool success) {
+  request *r = rp;
+  grpc_resolved_addresses *resolved =
+      grpc_blocking_resolve_address(r->name, r->default_port);
+  void *arg = r->arg;
+  grpc_resolve_cb cb = r->cb;
+  gpr_free(r->name);
+  gpr_free(r->default_port);
+  cb(exec_ctx, arg, resolved);
+  gpr_free(r);
+}
+
+void grpc_resolved_addresses_destroy(grpc_resolved_addresses *addrs) {
+  gpr_free(addrs->addrs);
+  gpr_free(addrs);
+}
+
+void grpc_resolve_address(const char *name, const char *default_port,
+                          grpc_resolve_cb cb, void *arg) {
+  request *r = gpr_malloc(sizeof(request));
+  grpc_closure_init(&r->request_closure, do_request_thread, r);
+  r->name = gpr_strdup(name);
+  r->default_port = gpr_strdup(default_port);
+  r->cb = cb;
+  r->arg = arg;
+  grpc_executor_enqueue(&r->request_closure, 1);
+}
+
+#endif
diff --git a/src/core/lib/iomgr/resolve_address_windows.c b/src/core/lib/iomgr/resolve_address_windows.c
new file mode 100644
index 0000000000..bde1f1b7f7
--- /dev/null
+++ b/src/core/lib/iomgr/resolve_address_windows.c
@@ -0,0 +1,169 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+#ifdef GPR_WINSOCK_SOCKET
+
+#include "src/core/lib/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+
+#include <string.h>
+#include <sys/types.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/host_port.h>
+#include <grpc/support/log.h>
+#include <grpc/support/log_win32.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/thd.h>
+#include <grpc/support/time.h>
+#include "src/core/lib/iomgr/executor.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/support/block_annotate.h"
+#include "src/core/lib/support/string.h"
+
+typedef struct {
+  char *name;
+  char *default_port;
+  grpc_resolve_cb cb;
+  grpc_closure request_closure;
+  void *arg;
+} request;
+
+static grpc_resolved_addresses *blocking_resolve_address_impl(
+    const char *name, const char *default_port) {
+  struct addrinfo hints;
+  struct addrinfo *result = NULL, *resp;
+  char *host;
+  char *port;
+  int s;
+  size_t i;
+  grpc_resolved_addresses *addrs = NULL;
+
+  /* parse name, splitting it into host and port parts */
+  gpr_split_host_port(name, &host, &port);
+  if (host == NULL) {
+    gpr_log(GPR_ERROR, "unparseable host:port: '%s'", name);
+    goto done;
+  }
+  if (port == NULL) {
+    if (default_port == NULL) {
+      gpr_log(GPR_ERROR, "no port in name '%s'", name);
+      goto done;
+    }
+    port = gpr_strdup(default_port);
+  }
+
+  /* Call getaddrinfo */
+  memset(&hints, 0, sizeof(hints));
+  hints.ai_family = AF_UNSPEC;     /* ipv4 or ipv6 */
+  hints.ai_socktype = SOCK_STREAM; /* stream socket */
+  hints.ai_flags = AI_PASSIVE;     /* for wildcard IP address */
+
+  GRPC_SCHEDULING_START_BLOCKING_REGION;
+  s = getaddrinfo(host, port, &hints, &result);
+  GRPC_SCHEDULING_END_BLOCKING_REGION;
+  if (s != 0) {
+    char *error_message = gpr_format_message(s);
+    gpr_log(GPR_ERROR, "getaddrinfo: %s", error_message);
+    gpr_free(error_message);
+    goto done;
+  }
+
+  /* Success path: set addrs non-NULL, fill it in */
+  addrs = gpr_malloc(sizeof(grpc_resolved_addresses));
+  addrs->naddrs = 0;
+  for (resp = result; resp != NULL; resp = resp->ai_next) {
+    addrs->naddrs++;
+  }
+  addrs->addrs = gpr_malloc(sizeof(grpc_resolved_address) * addrs->naddrs);
+  i = 0;
+  for (resp = result; resp != NULL; resp = resp->ai_next) {
+    memcpy(&addrs->addrs[i].addr, resp->ai_addr, resp->ai_addrlen);
+    addrs->addrs[i].len = resp->ai_addrlen;
+    i++;
+  }
+
+  {
+    for (i = 0; i < addrs->naddrs; i++) {
+      char *buf;
+      grpc_sockaddr_to_string(&buf, (struct sockaddr *)&addrs->addrs[i].addr,
+                              0);
+      gpr_free(buf);
+    }
+  }
+
+done:
+  gpr_free(host);
+  gpr_free(port);
+  if (result) {
+    freeaddrinfo(result);
+  }
+  return addrs;
+}
+
+grpc_resolved_addresses *(*grpc_blocking_resolve_address)(
+    const char *name, const char *default_port) = blocking_resolve_address_impl;
+
+/* Callback to be passed to grpc_executor to asynch-ify
+ * grpc_blocking_resolve_address */
+static void do_request_thread(grpc_exec_ctx *exec_ctx, void *rp, bool success) {
+  request *r = rp;
+  grpc_resolved_addresses *resolved =
+      grpc_blocking_resolve_address(r->name, r->default_port);
+  void *arg = r->arg;
+  grpc_resolve_cb cb = r->cb;
+  gpr_free(r->name);
+  gpr_free(r->default_port);
+  cb(exec_ctx, arg, resolved);
+  gpr_free(r);
+}
+
+void grpc_resolved_addresses_destroy(grpc_resolved_addresses *addrs) {
+  gpr_free(addrs->addrs);
+  gpr_free(addrs);
+}
+
+void grpc_resolve_address(const char *name, const char *default_port,
+                          grpc_resolve_cb cb, void *arg) {
+  request *r = gpr_malloc(sizeof(request));
+  grpc_closure_init(&r->request_closure, do_request_thread, r);
+  r->name = gpr_strdup(name);
+  r->default_port = gpr_strdup(default_port);
+  r->cb = cb;
+  r->arg = arg;
+  grpc_executor_enqueue(&r->request_closure, 1);
+}
+
+#endif
diff --git a/src/core/lib/iomgr/sockaddr.h b/src/core/lib/iomgr/sockaddr.h
new file mode 100644
index 0000000000..66a930ee6a
--- /dev/null
+++ b/src/core/lib/iomgr/sockaddr.h
@@ -0,0 +1,47 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_SOCKADDR_H
+#define GRPC_CORE_LIB_IOMGR_SOCKADDR_H
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WIN32
+#include "src/core/lib/iomgr/sockaddr_win32.h"
+#endif
+
+#ifdef GPR_POSIX_SOCKETADDR
+#include "src/core/lib/iomgr/sockaddr_posix.h"
+#endif
+
+#endif /* GRPC_CORE_LIB_IOMGR_SOCKADDR_H */
diff --git a/src/core/lib/iomgr/sockaddr_posix.h b/src/core/lib/iomgr/sockaddr_posix.h
new file mode 100644
index 0000000000..79a7467c5d
--- /dev/null
+++ b/src/core/lib/iomgr/sockaddr_posix.h
@@ -0,0 +1,44 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_SOCKADDR_POSIX_H
+#define GRPC_CORE_LIB_IOMGR_SOCKADDR_POSIX_H
+
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#endif /* GRPC_CORE_LIB_IOMGR_SOCKADDR_POSIX_H */
diff --git a/src/core/lib/iomgr/sockaddr_utils.c b/src/core/lib/iomgr/sockaddr_utils.c
new file mode 100644
index 0000000000..127d95c618
--- /dev/null
+++ b/src/core/lib/iomgr/sockaddr_utils.c
@@ -0,0 +1,227 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+
+#include <errno.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/host_port.h>
+#include <grpc/support/log.h>
+#include <grpc/support/port_platform.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+#include "src/core/lib/support/string.h"
+
+static const uint8_t kV4MappedPrefix[] = {0, 0, 0, 0, 0,    0,
+                                          0, 0, 0, 0, 0xff, 0xff};
+
+int grpc_sockaddr_is_v4mapped(const struct sockaddr *addr,
+                              struct sockaddr_in *addr4_out) {
+  GPR_ASSERT(addr != (struct sockaddr *)addr4_out);
+  if (addr->sa_family == AF_INET6) {
+    const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6 *)addr;
+    if (memcmp(addr6->sin6_addr.s6_addr, kV4MappedPrefix,
+               sizeof(kV4MappedPrefix)) == 0) {
+      if (addr4_out != NULL) {
+        /* Normalize ::ffff:0.0.0.0/96 to IPv4. */
+        memset(addr4_out, 0, sizeof(*addr4_out));
+        addr4_out->sin_family = AF_INET;
+        /* s6_addr32 would be nice, but it's non-standard. */
+        memcpy(&addr4_out->sin_addr, &addr6->sin6_addr.s6_addr[12], 4);
+        addr4_out->sin_port = addr6->sin6_port;
+      }
+      return 1;
+    }
+  }
+  return 0;
+}
+
+int grpc_sockaddr_to_v4mapped(const struct sockaddr *addr,
+                              struct sockaddr_in6 *addr6_out) {
+  GPR_ASSERT(addr != (struct sockaddr *)addr6_out);
+  if (addr->sa_family == AF_INET) {
+    const struct sockaddr_in *addr4 = (const struct sockaddr_in *)addr;
+    memset(addr6_out, 0, sizeof(*addr6_out));
+    addr6_out->sin6_family = AF_INET6;
+    memcpy(&addr6_out->sin6_addr.s6_addr[0], kV4MappedPrefix, 12);
+    memcpy(&addr6_out->sin6_addr.s6_addr[12], &addr4->sin_addr, 4);
+    addr6_out->sin6_port = addr4->sin_port;
+    return 1;
+  }
+  return 0;
+}
+
+int grpc_sockaddr_is_wildcard(const struct sockaddr *addr, int *port_out) {
+  struct sockaddr_in addr4_normalized;
+  if (grpc_sockaddr_is_v4mapped(addr, &addr4_normalized)) {
+    addr = (struct sockaddr *)&addr4_normalized;
+  }
+  if (addr->sa_family == AF_INET) {
+    /* Check for 0.0.0.0 */
+    const struct sockaddr_in *addr4 = (const struct sockaddr_in *)addr;
+    if (addr4->sin_addr.s_addr != 0) {
+      return 0;
+    }
+    *port_out = ntohs(addr4->sin_port);
+    return 1;
+  } else if (addr->sa_family == AF_INET6) {
+    /* Check for :: */
+    const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6 *)addr;
+    int i;
+    for (i = 0; i < 16; i++) {
+      if (addr6->sin6_addr.s6_addr[i] != 0) {
+        return 0;
+      }
+    }
+    *port_out = ntohs(addr6->sin6_port);
+    return 1;
+  } else {
+    return 0;
+  }
+}
+
+void grpc_sockaddr_make_wildcards(int port, struct sockaddr_in *wild4_out,
+                                  struct sockaddr_in6 *wild6_out) {
+  grpc_sockaddr_make_wildcard4(port, wild4_out);
+  grpc_sockaddr_make_wildcard6(port, wild6_out);
+}
+
+void grpc_sockaddr_make_wildcard4(int port, struct sockaddr_in *wild_out) {
+  GPR_ASSERT(port >= 0 && port < 65536);
+  memset(wild_out, 0, sizeof(*wild_out));
+  wild_out->sin_family = AF_INET;
+  wild_out->sin_port = htons((uint16_t)port);
+}
+
+void grpc_sockaddr_make_wildcard6(int port, struct sockaddr_in6 *wild_out) {
+  GPR_ASSERT(port >= 0 && port < 65536);
+  memset(wild_out, 0, sizeof(*wild_out));
+  wild_out->sin6_family = AF_INET6;
+  wild_out->sin6_port = htons((uint16_t)port);
+}
+
+int grpc_sockaddr_to_string(char **out, const struct sockaddr *addr,
+                            int normalize) {
+  const int save_errno = errno;
+  struct sockaddr_in addr_normalized;
+  char ntop_buf[INET6_ADDRSTRLEN];
+  const void *ip = NULL;
+  int port;
+  int ret;
+
+  *out = NULL;
+  if (normalize && grpc_sockaddr_is_v4mapped(addr, &addr_normalized)) {
+    addr = (const struct sockaddr *)&addr_normalized;
+  }
+  if (addr->sa_family == AF_INET) {
+    const struct sockaddr_in *addr4 = (const struct sockaddr_in *)addr;
+    ip = &addr4->sin_addr;
+    port = ntohs(addr4->sin_port);
+  } else if (addr->sa_family == AF_INET6) {
+    const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6 *)addr;
+    ip = &addr6->sin6_addr;
+    port = ntohs(addr6->sin6_port);
+  }
+  /* Windows inet_ntop wants a mutable ip pointer */
+  if (ip != NULL &&
+      inet_ntop(addr->sa_family, (void *)ip, ntop_buf, sizeof(ntop_buf)) !=
+          NULL) {
+    ret = gpr_join_host_port(out, ntop_buf, port);
+  } else {
+    ret = gpr_asprintf(out, "(sockaddr family=%d)", addr->sa_family);
+  }
+  /* This is probably redundant, but we wouldn't want to log the wrong error. */
+  errno = save_errno;
+  return ret;
+}
+
+char *grpc_sockaddr_to_uri(const struct sockaddr *addr) {
+  char *temp;
+  char *result;
+  struct sockaddr_in addr_normalized;
+
+  if (grpc_sockaddr_is_v4mapped(addr, &addr_normalized)) {
+    addr = (const struct sockaddr *)&addr_normalized;
+  }
+
+  switch (addr->sa_family) {
+    case AF_INET:
+      grpc_sockaddr_to_string(&temp, addr, 0);
+      gpr_asprintf(&result, "ipv4:%s", temp);
+      gpr_free(temp);
+      return result;
+    case AF_INET6:
+      grpc_sockaddr_to_string(&temp, addr, 0);
+      gpr_asprintf(&result, "ipv6:%s", temp);
+      gpr_free(temp);
+      return result;
+    default:
+      return grpc_sockaddr_to_uri_unix_if_possible(addr);
+  }
+}
+
+int grpc_sockaddr_get_port(const struct sockaddr *addr) {
+  switch (addr->sa_family) {
+    case AF_INET:
+      return ntohs(((struct sockaddr_in *)addr)->sin_port);
+    case AF_INET6:
+      return ntohs(((struct sockaddr_in6 *)addr)->sin6_port);
+    default:
+      if (grpc_is_unix_socket(addr)) {
+        return 1;
+      }
+      gpr_log(GPR_ERROR, "Unknown socket family %d in grpc_sockaddr_get_port",
+              addr->sa_family);
+      return 0;
+  }
+}
+
+int grpc_sockaddr_set_port(const struct sockaddr *addr, int port) {
+  switch (addr->sa_family) {
+    case AF_INET:
+      GPR_ASSERT(port >= 0 && port < 65536);
+      ((struct sockaddr_in *)addr)->sin_port = htons((uint16_t)port);
+      return 1;
+    case AF_INET6:
+      GPR_ASSERT(port >= 0 && port < 65536);
+      ((struct sockaddr_in6 *)addr)->sin6_port = htons((uint16_t)port);
+      return 1;
+    default:
+      gpr_log(GPR_ERROR, "Unknown socket family %d in grpc_sockaddr_set_port",
+              addr->sa_family);
+      return 0;
+  }
+}
diff --git a/src/core/lib/iomgr/sockaddr_utils.h b/src/core/lib/iomgr/sockaddr_utils.h
new file mode 100644
index 0000000000..20a3e3bec3
--- /dev/null
+++ b/src/core/lib/iomgr/sockaddr_utils.h
@@ -0,0 +1,89 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_SOCKADDR_UTILS_H
+#define GRPC_CORE_LIB_IOMGR_SOCKADDR_UTILS_H
+
+#include "src/core/lib/iomgr/sockaddr.h"
+
+/* Returns true if addr is an IPv4-mapped IPv6 address within the
+   ::ffff:0.0.0.0/96 range, or false otherwise.
+
+   If addr4_out is non-NULL, the inner IPv4 address will be copied here when
+   returning true. */
+int grpc_sockaddr_is_v4mapped(const struct sockaddr *addr,
+                              struct sockaddr_in *addr4_out);
+
+/* If addr is an AF_INET address, writes the corresponding ::ffff:0.0.0.0/96
+   address to addr6_out and returns true.  Otherwise returns false. */
+int grpc_sockaddr_to_v4mapped(const struct sockaddr *addr,
+                              struct sockaddr_in6 *addr6_out);
+
+/* If addr is ::, 0.0.0.0, or ::ffff:0.0.0.0, writes the port number to
+   *port_out (if not NULL) and returns true, otherwise returns false. */
+int grpc_sockaddr_is_wildcard(const struct sockaddr *addr, int *port_out);
+
+/* Writes 0.0.0.0:port and [::]:port to separate sockaddrs. */
+void grpc_sockaddr_make_wildcards(int port, struct sockaddr_in *wild4_out,
+                                  struct sockaddr_in6 *wild6_out);
+
+/* Writes 0.0.0.0:port. */
+void grpc_sockaddr_make_wildcard4(int port, struct sockaddr_in *wild_out);
+
+/* Writes [::]:port. */
+void grpc_sockaddr_make_wildcard6(int port, struct sockaddr_in6 *wild_out);
+
+/* Return the IP port number of a sockaddr */
+int grpc_sockaddr_get_port(const struct sockaddr *addr);
+
+/* Set IP port number of a sockaddr */
+int grpc_sockaddr_set_port(const struct sockaddr *addr, int port);
+
+/* Converts a sockaddr into a newly-allocated human-readable string.
+
+   Currently, only the AF_INET and AF_INET6 families are recognized.
+   If the normalize flag is enabled, ::ffff:0.0.0.0/96 IPv6 addresses are
+   displayed as plain IPv4.
+
+   Usage is similar to gpr_asprintf: returns the number of bytes written
+   (excluding the final '\0'), and *out points to a string which must later be
+   destroyed using gpr_free().
+
+   In the unlikely event of an error, returns -1 and sets *out to NULL.
+   The existing value of errno is always preserved. */
+int grpc_sockaddr_to_string(char **out, const struct sockaddr *addr,
+                            int normalize);
+
+char *grpc_sockaddr_to_uri(const struct sockaddr *addr);
+
+#endif /* GRPC_CORE_LIB_IOMGR_SOCKADDR_UTILS_H */
diff --git a/src/core/lib/iomgr/sockaddr_win32.h b/src/core/lib/iomgr/sockaddr_win32.h
new file mode 100644
index 0000000000..2dd7111240
--- /dev/null
+++ b/src/core/lib/iomgr/sockaddr_win32.h
@@ -0,0 +1,43 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_SOCKADDR_WIN32_H
+#define GRPC_CORE_LIB_IOMGR_SOCKADDR_WIN32_H
+
+#include <winsock2.h>
+#include <ws2tcpip.h>
+
+// must be included after the above
+#include <mswsock.h>
+
+#endif /* GRPC_CORE_LIB_IOMGR_SOCKADDR_WIN32_H */
diff --git a/src/core/lib/iomgr/socket_utils_common_posix.c b/src/core/lib/iomgr/socket_utils_common_posix.c
new file mode 100644
index 0000000000..9dbc2784e4
--- /dev/null
+++ b/src/core/lib/iomgr/socket_utils_common_posix.c
@@ -0,0 +1,208 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <grpc/support/host_port.h>
+#include <grpc/support/log.h>
+#include <grpc/support/port_platform.h>
+#include <grpc/support/sync.h>
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/support/string.h"
+
+/* set a socket to non blocking mode */
+int grpc_set_socket_nonblocking(int fd, int non_blocking) {
+  int oldflags = fcntl(fd, F_GETFL, 0);
+  if (oldflags < 0) {
+    return 0;
+  }
+
+  if (non_blocking) {
+    oldflags |= O_NONBLOCK;
+  } else {
+    oldflags &= ~O_NONBLOCK;
+  }
+
+  if (fcntl(fd, F_SETFL, oldflags) != 0) {
+    return 0;
+  }
+
+  return 1;
+}
+
+int grpc_set_socket_no_sigpipe_if_possible(int fd) {
+#ifdef GPR_HAVE_SO_NOSIGPIPE
+  int val = 1;
+  int newval;
+  socklen_t intlen = sizeof(newval);
+  return 0 == setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &val, sizeof(val)) &&
+         0 == getsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &newval, &intlen) &&
+         (newval != 0) == val;
+#else
+  return 1;
+#endif
+}
+
+/* set a socket to close on exec */
+int grpc_set_socket_cloexec(int fd, int close_on_exec) {
+  int oldflags = fcntl(fd, F_GETFD, 0);
+  if (oldflags < 0) {
+    return 0;
+  }
+
+  if (close_on_exec) {
+    oldflags |= FD_CLOEXEC;
+  } else {
+    oldflags &= ~FD_CLOEXEC;
+  }
+
+  if (fcntl(fd, F_SETFD, oldflags) != 0) {
+    return 0;
+  }
+
+  return 1;
+}
+
+/* set a socket to reuse old addresses */
+int grpc_set_socket_reuse_addr(int fd, int reuse) {
+  int val = (reuse != 0);
+  int newval;
+  socklen_t intlen = sizeof(newval);
+  return 0 == setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)) &&
+         0 == getsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &newval, &intlen) &&
+         (newval != 0) == val;
+}
+
+/* disable nagle */
+int grpc_set_socket_low_latency(int fd, int low_latency) {
+  int val = (low_latency != 0);
+  int newval;
+  socklen_t intlen = sizeof(newval);
+  return 0 == setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &val, sizeof(val)) &&
+         0 == getsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &newval, &intlen) &&
+         (newval != 0) == val;
+}
+
+static gpr_once g_probe_ipv6_once = GPR_ONCE_INIT;
+static int g_ipv6_loopback_available;
+
+static void probe_ipv6_once(void) {
+  int fd = socket(AF_INET6, SOCK_STREAM, 0);
+  g_ipv6_loopback_available = 0;
+  if (fd < 0) {
+    gpr_log(GPR_INFO, "Disabling AF_INET6 sockets because socket() failed.");
+  } else {
+    struct sockaddr_in6 addr;
+    memset(&addr, 0, sizeof(addr));
+    addr.sin6_family = AF_INET6;
+    addr.sin6_addr.s6_addr[15] = 1; /* [::1]:0 */
+    if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) == 0) {
+      g_ipv6_loopback_available = 1;
+    } else {
+      gpr_log(GPR_INFO,
+              "Disabling AF_INET6 sockets because ::1 is not available.");
+    }
+    close(fd);
+  }
+}
+
+int grpc_ipv6_loopback_available(void) {
+  gpr_once_init(&g_probe_ipv6_once, probe_ipv6_once);
+  return g_ipv6_loopback_available;
+}
+
+/* This should be 0 in production, but it may be enabled for testing or
+   debugging purposes, to simulate an environment where IPv6 sockets can't
+   also speak IPv4. */
+int grpc_forbid_dualstack_sockets_for_testing = 0;
+
+static int set_socket_dualstack(int fd) {
+  if (!grpc_forbid_dualstack_sockets_for_testing) {
+    const int off = 0;
+    return 0 == setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &off, sizeof(off));
+  } else {
+    /* Force an IPv6-only socket, for testing purposes. */
+    const int on = 1;
+    setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
+    return 0;
+  }
+}
+
+int grpc_create_dualstack_socket(const struct sockaddr *addr, int type,
+                                 int protocol, grpc_dualstack_mode *dsmode) {
+  int family = addr->sa_family;
+  if (family == AF_INET6) {
+    int fd;
+    if (grpc_ipv6_loopback_available()) {
+      fd = socket(family, type, protocol);
+    } else {
+      fd = -1;
+      errno = EAFNOSUPPORT;
+    }
+    /* Check if we've got a valid dualstack socket. */
+    if (fd >= 0 && set_socket_dualstack(fd)) {
+      *dsmode = GRPC_DSMODE_DUALSTACK;
+      return fd;
+    }
+    /* If this isn't an IPv4 address, then return whatever we've got. */
+    if (!grpc_sockaddr_is_v4mapped(addr, NULL)) {
+      *dsmode = GRPC_DSMODE_IPV6;
+      return fd;
+    }
+    /* Fall back to AF_INET. */
+    if (fd >= 0) {
+      close(fd);
+    }
+    family = AF_INET;
+  }
+  *dsmode = family == AF_INET ? GRPC_DSMODE_IPV4 : GRPC_DSMODE_NONE;
+  return socket(family, type, protocol);
+}
+
+#endif
diff --git a/src/core/lib/iomgr/socket_utils_linux.c b/src/core/lib/iomgr/socket_utils_linux.c
new file mode 100644
index 0000000000..e7dfe892ca
--- /dev/null
+++ b/src/core/lib/iomgr/socket_utils_linux.c
@@ -0,0 +1,51 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_LINUX_SOCKETUTILS
+
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+
+#include <sys/socket.h>
+#include <sys/types.h>
+
+int grpc_accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen,
+                 int nonblock, int cloexec) {
+  int flags = 0;
+  flags |= nonblock ? SOCK_NONBLOCK : 0;
+  flags |= cloexec ? SOCK_CLOEXEC : 0;
+  return accept4(sockfd, addr, addrlen, flags);
+}
+
+#endif
diff --git a/src/core/lib/iomgr/socket_utils_posix.c b/src/core/lib/iomgr/socket_utils_posix.c
new file mode 100644
index 0000000000..b2fa00c5c1
--- /dev/null
+++ b/src/core/lib/iomgr/socket_utils_posix.c
@@ -0,0 +1,70 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKETUTILS
+
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include <grpc/support/log.h>
+
+int grpc_accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen,
+                 int nonblock, int cloexec) {
+  int fd, flags;
+
+  fd = accept(sockfd, addr, addrlen);
+  if (fd >= 0) {
+    if (nonblock) {
+      flags = fcntl(fd, F_GETFL, 0);
+      if (flags < 0) goto close_and_error;
+      if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) != 0) goto close_and_error;
+    }
+    if (cloexec) {
+      flags = fcntl(fd, F_GETFD, 0);
+      if (flags < 0) goto close_and_error;
+      if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) != 0) goto close_and_error;
+    }
+  }
+  return fd;
+
+close_and_error:
+  close(fd);
+  return -1;
+}
+
+#endif /* GPR_POSIX_SOCKETUTILS */
diff --git a/src/core/lib/iomgr/socket_utils_posix.h b/src/core/lib/iomgr/socket_utils_posix.h
new file mode 100644
index 0000000000..063f298d72
--- /dev/null
+++ b/src/core/lib/iomgr/socket_utils_posix.h
@@ -0,0 +1,113 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_SOCKET_UTILS_POSIX_H
+#define GRPC_CORE_LIB_IOMGR_SOCKET_UTILS_POSIX_H
+
+#include <sys/socket.h>
+#include <unistd.h>
+
+/* a wrapper for accept or accept4 */
+int grpc_accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen,
+                 int nonblock, int cloexec);
+
+/* set a socket to non blocking mode */
+int grpc_set_socket_nonblocking(int fd, int non_blocking);
+
+/* set a socket to close on exec */
+int grpc_set_socket_cloexec(int fd, int close_on_exec);
+
+/* set a socket to reuse old addresses */
+int grpc_set_socket_reuse_addr(int fd, int reuse);
+
+/* disable nagle */
+int grpc_set_socket_low_latency(int fd, int low_latency);
+
+/* Returns true if this system can create AF_INET6 sockets bound to ::1.
+   The value is probed once, and cached for the life of the process.
+
+   This is more restrictive than checking for socket(AF_INET6) to succeed,
+   because Linux with "net.ipv6.conf.all.disable_ipv6 = 1" is able to create
+   and bind IPv6 sockets, but cannot connect to a getsockname() of [::]:port
+   without a valid loopback interface.  Rather than expose this half-broken
+   state to library users, we turn off IPv6 sockets. */
+int grpc_ipv6_loopback_available(void);
+
+/* Tries to set SO_NOSIGPIPE if available on this platform.
+   Returns 1 on success, 0 on failure.
+   If SO_NO_SIGPIPE is not available, returns 1. */
+int grpc_set_socket_no_sigpipe_if_possible(int fd);
+
+/* An enum to keep track of IPv4/IPv6 socket modes.
+
+   Currently, this information is only used when a socket is first created, but
+   in the future we may wish to store it alongside the fd.  This would let calls
+   like sendto() know which family to use without asking the kernel first. */
+typedef enum grpc_dualstack_mode {
+  /* Uninitialized, or a non-IP socket. */
+  GRPC_DSMODE_NONE,
+  /* AF_INET only. */
+  GRPC_DSMODE_IPV4,
+  /* AF_INET6 only, because IPV6_V6ONLY could not be cleared. */
+  GRPC_DSMODE_IPV6,
+  /* AF_INET6, which also supports ::ffff-mapped IPv4 addresses. */
+  GRPC_DSMODE_DUALSTACK
+} grpc_dualstack_mode;
+
+/* Only tests should use this flag. */
+extern int grpc_forbid_dualstack_sockets_for_testing;
+
+/* Creates a new socket for connecting to (or listening on) an address.
+
+   If addr is AF_INET6, this creates an IPv6 socket first.  If that fails,
+   and addr is within ::ffff:0.0.0.0/96, then it automatically falls back to
+   an IPv4 socket.
+
+   If addr is AF_INET, AF_UNIX, or anything else, then this is similar to
+   calling socket() directly.
+
+   Returns an fd on success, otherwise returns -1 with errno set to the result
+   of a failed socket() call.
+
+   The *dsmode output indicates which address family was actually created.
+   The recommended way to use this is:
+   - First convert to IPv6 using grpc_sockaddr_to_v4mapped().
+   - Create the socket.
+   - If *dsmode is IPV4, use grpc_sockaddr_is_v4mapped() to convert back to
+     IPv4, so that bind() or connect() see the correct family.
+   Also, it's important to distinguish between DUALSTACK and IPV6 when
+   listening on the [::] wildcard address. */
+int grpc_create_dualstack_socket(const struct sockaddr *addr, int type,
+                                 int protocol, grpc_dualstack_mode *dsmode);
+
+#endif /* GRPC_CORE_LIB_IOMGR_SOCKET_UTILS_POSIX_H */
diff --git a/src/core/lib/iomgr/socket_windows.c b/src/core/lib/iomgr/socket_windows.c
new file mode 100644
index 0000000000..1023a6d4f8
--- /dev/null
+++ b/src/core/lib/iomgr/socket_windows.c
@@ -0,0 +1,100 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include <winsock2.h>
+
+// must be included after winsock2.h
+#include <mswsock.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/log_win32.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/iomgr/iocp_windows.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/pollset.h"
+#include "src/core/lib/iomgr/pollset_windows.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+
+grpc_winsocket *grpc_winsocket_create(SOCKET socket, const char *name) {
+  char *final_name;
+  grpc_winsocket *r = gpr_malloc(sizeof(grpc_winsocket));
+  memset(r, 0, sizeof(grpc_winsocket));
+  r->socket = socket;
+  gpr_mu_init(&r->state_mu);
+  gpr_asprintf(&final_name, "%s:socket=0x%p", name, r);
+  grpc_iomgr_register_object(&r->iomgr_object, final_name);
+  gpr_free(final_name);
+  grpc_iocp_add_socket(r);
+  return r;
+}
+
+/* Schedule a shutdown of the socket operations. Will call the pending
+   operations to abort them. We need to do that this way because of the
+   various callsites of that function, which happens to be in various
+   mutex hold states, and that'd be unsafe to call them directly. */
+void grpc_winsocket_shutdown(grpc_winsocket *winsocket) {
+  /* Grab the function pointer for DisconnectEx for that specific socket.
+     It may change depending on the interface. */
+  int status;
+  GUID guid = WSAID_DISCONNECTEX;
+  LPFN_DISCONNECTEX DisconnectEx;
+  DWORD ioctl_num_bytes;
+
+  status = WSAIoctl(winsocket->socket, SIO_GET_EXTENSION_FUNCTION_POINTER,
+                    &guid, sizeof(guid), &DisconnectEx, sizeof(DisconnectEx),
+                    &ioctl_num_bytes, NULL, NULL);
+
+  if (status == 0) {
+    DisconnectEx(winsocket->socket, NULL, 0, 0);
+  } else {
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    gpr_log(GPR_ERROR, "Unable to retrieve DisconnectEx pointer : %s",
+            utf8_message);
+    gpr_free(utf8_message);
+  }
+  closesocket(winsocket->socket);
+}
+
+void grpc_winsocket_destroy(grpc_winsocket *winsocket) {
+  grpc_iomgr_unregister_object(&winsocket->iomgr_object);
+  gpr_mu_destroy(&winsocket->state_mu);
+  gpr_free(winsocket);
+}
+
+#endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/socket_windows.h b/src/core/lib/iomgr/socket_windows.h
new file mode 100644
index 0000000000..74447896c9
--- /dev/null
+++ b/src/core/lib/iomgr/socket_windows.h
@@ -0,0 +1,111 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_SOCKET_WINDOWS_H
+#define GRPC_CORE_LIB_IOMGR_SOCKET_WINDOWS_H
+
+#include <grpc/support/port_platform.h>
+#include <winsock2.h>
+
+#include <grpc/support/atm.h>
+#include <grpc/support/sync.h>
+
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+
+/* This holds the data for an outstanding read or write on a socket.
+   The mutex to protect the concurrent access to that data is the one
+   inside the winsocket wrapper. */
+typedef struct grpc_winsocket_callback_info {
+  /* This is supposed to be a WSAOVERLAPPED, but in order to get that
+     definition, we need to include ws2tcpip.h, which needs to be included
+     from the top, otherwise it'll clash with a previous inclusion of
+     windows.h that in turns includes winsock.h. If anyone knows a way
+     to do it properly, feel free to send a patch. */
+  OVERLAPPED overlapped;
+  /* The callback information for the pending operation. May be empty if the
+     caller hasn't registered a callback yet. */
+  grpc_closure *closure;
+  /* A boolean to describe if the IO Completion Port got a notification for
+     that operation. This will happen if the operation completed before the
+     called had time to register a callback. We could avoid that behavior
+     altogether by forcing the caller to always register its callback before
+     proceeding queue an operation, but it is frequent for an IO Completion
+     Port to trigger quickly. This way we avoid a context switch for calling
+     the callback. We also simplify the read / write operations to avoid having
+     to hold a mutex for a long amount of time. */
+  int has_pending_iocp;
+  /* The results of the overlapped operation. */
+  DWORD bytes_transfered;
+  int wsa_error;
+} grpc_winsocket_callback_info;
+
+/* This is a wrapper to a Windows socket. A socket can have one outstanding
+   read, and one outstanding write. Doing an asynchronous accept means waiting
+   for a read operation. Doing an asynchronous connect means waiting for a
+   write operation. These are completely arbitrary ties between the operation
+   and the kind of event, because we can have one overlapped per pending
+   operation, whichever its nature is. So we could have more dedicated pending
+   operation callbacks for connect and listen. But given the scope of listen
+   and accept, we don't need to go to that extent and waste memory. Also, this
+   is closer to what happens in posix world. */
+typedef struct grpc_winsocket {
+  SOCKET socket;
+
+  grpc_winsocket_callback_info write_info;
+  grpc_winsocket_callback_info read_info;
+
+  gpr_mu state_mu;
+
+  /* You can't add the same socket twice to the same IO Completion Port.
+     This prevents that. */
+  int added_to_iocp;
+
+  grpc_closure shutdown_closure;
+
+  /* A label for iomgr to track outstanding objects */
+  grpc_iomgr_object iomgr_object;
+} grpc_winsocket;
+
+/* Create a wrapped windows handle. This takes ownership of it, meaning that
+   it will be responsible for closing it. */
+grpc_winsocket *grpc_winsocket_create(SOCKET socket, const char *name);
+
+/* Initiate an asynchronous shutdown of the socket. Will call off any pending
+   operation to cancel them. */
+void grpc_winsocket_shutdown(grpc_winsocket *socket);
+
+/* Destroy a socket. Should only be called if there's no pending operation. */
+void grpc_winsocket_destroy(grpc_winsocket *socket);
+
+#endif /* GRPC_CORE_LIB_IOMGR_SOCKET_WINDOWS_H */
diff --git a/src/core/lib/iomgr/tcp_client.h b/src/core/lib/iomgr/tcp_client.h
new file mode 100644
index 0000000000..6bbe26445a
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_client.h
@@ -0,0 +1,53 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_TCP_CLIENT_H
+#define GRPC_CORE_LIB_IOMGR_TCP_CLIENT_H
+
+#include <grpc/support/time.h>
+#include "src/core/lib/iomgr/endpoint.h"
+#include "src/core/lib/iomgr/pollset_set.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+
+/* Asynchronously connect to an address (specified as (addr, len)), and call
+   cb with arg and the completed connection when done (or call cb with arg and
+   NULL on failure).
+   interested_parties points to a set of pollsets that would be interested
+   in this connection being established (in order to continue their work) */
+void grpc_tcp_client_connect(grpc_exec_ctx *exec_ctx, grpc_closure *on_connect,
+                             grpc_endpoint **endpoint,
+                             grpc_pollset_set *interested_parties,
+                             const struct sockaddr *addr, size_t addr_len,
+                             gpr_timespec deadline);
+
+#endif /* GRPC_CORE_LIB_IOMGR_TCP_CLIENT_H */
diff --git a/src/core/lib/iomgr/tcp_client_posix.c b/src/core/lib/iomgr/tcp_client_posix.c
new file mode 100644
index 0000000000..5f948d0d19
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_client_posix.c
@@ -0,0 +1,306 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/tcp_client.h"
+
+#include <errno.h>
+#include <netinet/in.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/time.h>
+
+#include "src/core/lib/iomgr/ev_posix.h"
+#include "src/core/lib/iomgr/iomgr_posix.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+#include "src/core/lib/iomgr/tcp_posix.h"
+#include "src/core/lib/iomgr/timer.h"
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+#include "src/core/lib/support/string.h"
+
+extern int grpc_tcp_trace;
+
+typedef struct {
+  gpr_mu mu;
+  grpc_fd *fd;
+  gpr_timespec deadline;
+  grpc_timer alarm;
+  int refs;
+  grpc_closure write_closure;
+  grpc_pollset_set *interested_parties;
+  char *addr_str;
+  grpc_endpoint **ep;
+  grpc_closure *closure;
+} async_connect;
+
+static int prepare_socket(const struct sockaddr *addr, int fd) {
+  if (fd < 0) {
+    goto error;
+  }
+
+  if (!grpc_set_socket_nonblocking(fd, 1) || !grpc_set_socket_cloexec(fd, 1) ||
+      (!grpc_is_unix_socket(addr) && !grpc_set_socket_low_latency(fd, 1)) ||
+      !grpc_set_socket_no_sigpipe_if_possible(fd)) {
+    gpr_log(GPR_ERROR, "Unable to configure socket %d: %s", fd,
+            strerror(errno));
+    goto error;
+  }
+  return 1;
+
+error:
+  if (fd >= 0) {
+    close(fd);
+  }
+  return 0;
+}
+
+static void tc_on_alarm(grpc_exec_ctx *exec_ctx, void *acp, bool success) {
+  int done;
+  async_connect *ac = acp;
+  if (grpc_tcp_trace) {
+    gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: on_alarm: success=%d", ac->addr_str,
+            success);
+  }
+  gpr_mu_lock(&ac->mu);
+  if (ac->fd != NULL) {
+    grpc_fd_shutdown(exec_ctx, ac->fd);
+  }
+  done = (--ac->refs == 0);
+  gpr_mu_unlock(&ac->mu);
+  if (done) {
+    gpr_mu_destroy(&ac->mu);
+    gpr_free(ac->addr_str);
+    gpr_free(ac);
+  }
+}
+
+static void on_writable(grpc_exec_ctx *exec_ctx, void *acp, bool success) {
+  async_connect *ac = acp;
+  int so_error = 0;
+  socklen_t so_error_size;
+  int err;
+  int done;
+  grpc_endpoint **ep = ac->ep;
+  grpc_closure *closure = ac->closure;
+  grpc_fd *fd;
+
+  if (grpc_tcp_trace) {
+    gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: on_writable: success=%d",
+            ac->addr_str, success);
+  }
+
+  gpr_mu_lock(&ac->mu);
+  GPR_ASSERT(ac->fd);
+  fd = ac->fd;
+  ac->fd = NULL;
+  gpr_mu_unlock(&ac->mu);
+
+  grpc_timer_cancel(exec_ctx, &ac->alarm);
+
+  gpr_mu_lock(&ac->mu);
+  if (success) {
+    do {
+      so_error_size = sizeof(so_error);
+      err = getsockopt(grpc_fd_wrapped_fd(fd), SOL_SOCKET, SO_ERROR, &so_error,
+                       &so_error_size);
+    } while (err < 0 && errno == EINTR);
+    if (err < 0) {
+      gpr_log(GPR_ERROR, "failed to connect to '%s': getsockopt(ERROR): %s",
+              ac->addr_str, strerror(errno));
+      goto finish;
+    } else if (so_error != 0) {
+      if (so_error == ENOBUFS) {
+        /* We will get one of these errors if we have run out of
+           memory in the kernel for the data structures allocated
+           when you connect a socket.  If this happens it is very
+           likely that if we wait a little bit then try again the
+           connection will work (since other programs or this
+           program will close their network connections and free up
+           memory).  This does _not_ indicate that there is anything
+           wrong with the server we are connecting to, this is a
+           local problem.
+
+           If you are looking at this code, then chances are that
+           your program or another program on the same computer
+           opened too many network connections.  The "easy" fix:
+           don't do that! */
+        gpr_log(GPR_ERROR, "kernel out of buffers");
+        gpr_mu_unlock(&ac->mu);
+        grpc_fd_notify_on_write(exec_ctx, fd, &ac->write_closure);
+        return;
+      } else {
+        switch (so_error) {
+          case ECONNREFUSED:
+            gpr_log(
+                GPR_ERROR,
+                "failed to connect to '%s': socket error: connection refused",
+                ac->addr_str);
+            break;
+          default:
+            gpr_log(GPR_ERROR, "failed to connect to '%s': socket error: %d",
+                    ac->addr_str, so_error);
+            break;
+        }
+        goto finish;
+      }
+    } else {
+      grpc_pollset_set_del_fd(exec_ctx, ac->interested_parties, fd);
+      *ep = grpc_tcp_create(fd, GRPC_TCP_DEFAULT_READ_SLICE_SIZE, ac->addr_str);
+      fd = NULL;
+      goto finish;
+    }
+  } else {
+    gpr_log(GPR_ERROR, "failed to connect to '%s': timeout occurred",
+            ac->addr_str);
+    goto finish;
+  }
+
+  GPR_UNREACHABLE_CODE(return );
+
+finish:
+  if (fd != NULL) {
+    grpc_pollset_set_del_fd(exec_ctx, ac->interested_parties, fd);
+    grpc_fd_orphan(exec_ctx, fd, NULL, NULL, "tcp_client_orphan");
+    fd = NULL;
+  }
+  done = (--ac->refs == 0);
+  gpr_mu_unlock(&ac->mu);
+  if (done) {
+    gpr_mu_destroy(&ac->mu);
+    gpr_free(ac->addr_str);
+    gpr_free(ac);
+  }
+  grpc_exec_ctx_enqueue(exec_ctx, closure, *ep != NULL, NULL);
+}
+
+void grpc_tcp_client_connect(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
+                             grpc_endpoint **ep,
+                             grpc_pollset_set *interested_parties,
+                             const struct sockaddr *addr, size_t addr_len,
+                             gpr_timespec deadline) {
+  int fd;
+  grpc_dualstack_mode dsmode;
+  int err;
+  async_connect *ac;
+  struct sockaddr_in6 addr6_v4mapped;
+  struct sockaddr_in addr4_copy;
+  grpc_fd *fdobj;
+  char *name;
+  char *addr_str;
+
+  *ep = NULL;
+
+  /* Use dualstack sockets where available. */
+  if (grpc_sockaddr_to_v4mapped(addr, &addr6_v4mapped)) {
+    addr = (const struct sockaddr *)&addr6_v4mapped;
+    addr_len = sizeof(addr6_v4mapped);
+  }
+
+  fd = grpc_create_dualstack_socket(addr, SOCK_STREAM, 0, &dsmode);
+  if (fd < 0) {
+    gpr_log(GPR_ERROR, "Unable to create socket: %s", strerror(errno));
+  }
+  if (dsmode == GRPC_DSMODE_IPV4) {
+    /* If we got an AF_INET socket, map the address back to IPv4. */
+    GPR_ASSERT(grpc_sockaddr_is_v4mapped(addr, &addr4_copy));
+    addr = (struct sockaddr *)&addr4_copy;
+    addr_len = sizeof(addr4_copy);
+  }
+  if (!prepare_socket(addr, fd)) {
+    grpc_exec_ctx_enqueue(exec_ctx, closure, false, NULL);
+    return;
+  }
+
+  do {
+    GPR_ASSERT(addr_len < ~(socklen_t)0);
+    err = connect(fd, addr, (socklen_t)addr_len);
+  } while (err < 0 && errno == EINTR);
+
+  addr_str = grpc_sockaddr_to_uri(addr);
+  gpr_asprintf(&name, "tcp-client:%s", addr_str);
+
+  fdobj = grpc_fd_create(fd, name);
+
+  if (err >= 0) {
+    *ep = grpc_tcp_create(fdobj, GRPC_TCP_DEFAULT_READ_SLICE_SIZE, addr_str);
+    grpc_exec_ctx_enqueue(exec_ctx, closure, true, NULL);
+    goto done;
+  }
+
+  if (errno != EWOULDBLOCK && errno != EINPROGRESS) {
+    gpr_log(GPR_ERROR, "connect error to '%s': %s", addr_str, strerror(errno));
+    grpc_fd_orphan(exec_ctx, fdobj, NULL, NULL, "tcp_client_connect_error");
+    grpc_exec_ctx_enqueue(exec_ctx, closure, false, NULL);
+    goto done;
+  }
+
+  grpc_pollset_set_add_fd(exec_ctx, interested_parties, fdobj);
+
+  ac = gpr_malloc(sizeof(async_connect));
+  ac->closure = closure;
+  ac->ep = ep;
+  ac->fd = fdobj;
+  ac->interested_parties = interested_parties;
+  ac->addr_str = addr_str;
+  addr_str = NULL;
+  gpr_mu_init(&ac->mu);
+  ac->refs = 2;
+  ac->write_closure.cb = on_writable;
+  ac->write_closure.cb_arg = ac;
+
+  if (grpc_tcp_trace) {
+    gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: asynchronously connecting",
+            ac->addr_str);
+  }
+
+  gpr_mu_lock(&ac->mu);
+  grpc_timer_init(exec_ctx, &ac->alarm,
+                  gpr_convert_clock_type(deadline, GPR_CLOCK_MONOTONIC),
+                  tc_on_alarm, ac, gpr_now(GPR_CLOCK_MONOTONIC));
+  grpc_fd_notify_on_write(exec_ctx, ac->fd, &ac->write_closure);
+  gpr_mu_unlock(&ac->mu);
+
+done:
+  gpr_free(name);
+  gpr_free(addr_str);
+}
+
+#endif
diff --git a/src/core/lib/iomgr/tcp_client_windows.c b/src/core/lib/iomgr/tcp_client_windows.c
new file mode 100644
index 0000000000..86b8d58975
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_client_windows.c
@@ -0,0 +1,221 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include "src/core/lib/iomgr/sockaddr_win32.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/log_win32.h>
+#include <grpc/support/slice_buffer.h>
+#include <grpc/support/useful.h>
+
+#include "src/core/lib/iomgr/iocp_windows.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+#include "src/core/lib/iomgr/tcp_client.h"
+#include "src/core/lib/iomgr/tcp_windows.h"
+#include "src/core/lib/iomgr/timer.h"
+
+typedef struct {
+  grpc_closure *on_done;
+  gpr_mu mu;
+  grpc_winsocket *socket;
+  gpr_timespec deadline;
+  grpc_timer alarm;
+  char *addr_name;
+  int refs;
+  grpc_closure on_connect;
+  grpc_endpoint **endpoint;
+} async_connect;
+
+static void async_connect_unlock_and_cleanup(async_connect *ac) {
+  int done = (--ac->refs == 0);
+  gpr_mu_unlock(&ac->mu);
+  if (done) {
+    if (ac->socket != NULL) grpc_winsocket_destroy(ac->socket);
+    gpr_mu_destroy(&ac->mu);
+    gpr_free(ac->addr_name);
+    gpr_free(ac);
+  }
+}
+
+static void on_alarm(grpc_exec_ctx *exec_ctx, void *acp, bool occured) {
+  async_connect *ac = acp;
+  gpr_mu_lock(&ac->mu);
+  /* If the alarm didn't occur, it got cancelled. */
+  if (ac->socket != NULL && occured) {
+    grpc_winsocket_shutdown(ac->socket);
+  }
+  async_connect_unlock_and_cleanup(ac);
+}
+
+static void on_connect(grpc_exec_ctx *exec_ctx, void *acp, bool from_iocp) {
+  async_connect *ac = acp;
+  SOCKET sock = ac->socket->socket;
+  grpc_endpoint **ep = ac->endpoint;
+  grpc_winsocket_callback_info *info = &ac->socket->write_info;
+  grpc_closure *on_done = ac->on_done;
+
+  grpc_timer_cancel(exec_ctx, &ac->alarm);
+
+  gpr_mu_lock(&ac->mu);
+
+  if (from_iocp) {
+    DWORD transfered_bytes = 0;
+    DWORD flags;
+    BOOL wsa_success = WSAGetOverlappedResult(sock, &info->overlapped,
+                                              &transfered_bytes, FALSE, &flags);
+    GPR_ASSERT(transfered_bytes == 0);
+    if (!wsa_success) {
+      char *utf8_message = gpr_format_message(WSAGetLastError());
+      gpr_log(GPR_ERROR, "on_connect error: %s", utf8_message);
+      gpr_free(utf8_message);
+    } else {
+      *ep = grpc_tcp_create(ac->socket, ac->addr_name);
+      ac->socket = NULL;
+    }
+  }
+
+  async_connect_unlock_and_cleanup(ac);
+  /* If the connection was aborted, the callback was already called when
+     the deadline was met. */
+  on_done->cb(exec_ctx, on_done->cb_arg, *ep != NULL);
+}
+
+/* Tries to issue one async connection, then schedules both an IOCP
+   notification request for the connection, and one timeout alert. */
+void grpc_tcp_client_connect(grpc_exec_ctx *exec_ctx, grpc_closure *on_done,
+                             grpc_endpoint **endpoint,
+                             grpc_pollset_set *interested_parties,
+                             const struct sockaddr *addr, size_t addr_len,
+                             gpr_timespec deadline) {
+  SOCKET sock = INVALID_SOCKET;
+  BOOL success;
+  int status;
+  struct sockaddr_in6 addr6_v4mapped;
+  struct sockaddr_in6 local_address;
+  async_connect *ac;
+  grpc_winsocket *socket = NULL;
+  LPFN_CONNECTEX ConnectEx;
+  GUID guid = WSAID_CONNECTEX;
+  DWORD ioctl_num_bytes;
+  const char *message = NULL;
+  char *utf8_message;
+  grpc_winsocket_callback_info *info;
+
+  *endpoint = NULL;
+
+  /* Use dualstack sockets where available. */
+  if (grpc_sockaddr_to_v4mapped(addr, &addr6_v4mapped)) {
+    addr = (const struct sockaddr *)&addr6_v4mapped;
+    addr_len = sizeof(addr6_v4mapped);
+  }
+
+  sock = WSASocket(AF_INET6, SOCK_STREAM, IPPROTO_TCP, NULL, 0,
+                   WSA_FLAG_OVERLAPPED);
+  if (sock == INVALID_SOCKET) {
+    message = "Unable to create socket: %s";
+    goto failure;
+  }
+
+  if (!grpc_tcp_prepare_socket(sock)) {
+    message = "Unable to set socket options: %s";
+    goto failure;
+  }
+
+  /* Grab the function pointer for ConnectEx for that specific socket.
+     It may change depending on the interface. */
+  status =
+      WSAIoctl(sock, SIO_GET_EXTENSION_FUNCTION_POINTER, &guid, sizeof(guid),
+               &ConnectEx, sizeof(ConnectEx), &ioctl_num_bytes, NULL, NULL);
+
+  if (status != 0) {
+    message = "Unable to retrieve ConnectEx pointer: %s";
+    goto failure;
+  }
+
+  grpc_sockaddr_make_wildcard6(0, &local_address);
+
+  status = bind(sock, (struct sockaddr *)&local_address, sizeof(local_address));
+  if (status != 0) {
+    message = "Unable to bind socket: %s";
+    goto failure;
+  }
+
+  socket = grpc_winsocket_create(sock, "client");
+  info = &socket->write_info;
+  success =
+      ConnectEx(sock, addr, (int)addr_len, NULL, 0, NULL, &info->overlapped);
+
+  /* It wouldn't be unusual to get a success immediately. But we'll still get
+     an IOCP notification, so let's ignore it. */
+  if (!success) {
+    int error = WSAGetLastError();
+    if (error != ERROR_IO_PENDING) {
+      message = "ConnectEx failed: %s";
+      goto failure;
+    }
+  }
+
+  ac = gpr_malloc(sizeof(async_connect));
+  ac->on_done = on_done;
+  ac->socket = socket;
+  gpr_mu_init(&ac->mu);
+  ac->refs = 2;
+  ac->addr_name = grpc_sockaddr_to_uri(addr);
+  ac->endpoint = endpoint;
+  grpc_closure_init(&ac->on_connect, on_connect, ac);
+
+  grpc_timer_init(exec_ctx, &ac->alarm, deadline, on_alarm, ac,
+                  gpr_now(GPR_CLOCK_MONOTONIC));
+  grpc_socket_notify_on_write(exec_ctx, socket, &ac->on_connect);
+  return;
+
+failure:
+  utf8_message = gpr_format_message(WSAGetLastError());
+  gpr_log(GPR_ERROR, message, utf8_message);
+  gpr_free(utf8_message);
+  if (socket != NULL) {
+    grpc_winsocket_destroy(socket);
+  } else if (sock != INVALID_SOCKET) {
+    closesocket(sock);
+  }
+  grpc_exec_ctx_enqueue(exec_ctx, on_done, false, NULL);
+}
+
+#endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/tcp_posix.c b/src/core/lib/iomgr/tcp_posix.c
new file mode 100644
index 0000000000..64ccaf92ff
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_posix.c
@@ -0,0 +1,492 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/tcp_posix.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/slice.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/time.h>
+
+#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/iomgr/ev_posix.h"
+#include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/support/string.h"
+
+#ifdef GPR_HAVE_MSG_NOSIGNAL
+#define SENDMSG_FLAGS MSG_NOSIGNAL
+#else
+#define SENDMSG_FLAGS 0
+#endif
+
+#ifdef GPR_MSG_IOVLEN_TYPE
+typedef GPR_MSG_IOVLEN_TYPE msg_iovlen_type;
+#else
+typedef size_t msg_iovlen_type;
+#endif
+
+int grpc_tcp_trace = 0;
+
+typedef struct {
+  grpc_endpoint base;
+  grpc_fd *em_fd;
+  int fd;
+  int finished_edge;
+  msg_iovlen_type iov_size; /* Number of slices to allocate per read attempt */
+  size_t slice_size;
+  gpr_refcount refcount;
+
+  /* garbage after the last read */
+  gpr_slice_buffer last_read_buffer;
+
+  gpr_slice_buffer *incoming_buffer;
+  gpr_slice_buffer *outgoing_buffer;
+  /** slice within outgoing_buffer to write next */
+  size_t outgoing_slice_idx;
+  /** byte within outgoing_buffer->slices[outgoing_slice_idx] to write next */
+  size_t outgoing_byte_idx;
+
+  grpc_closure *read_cb;
+  grpc_closure *write_cb;
+  grpc_closure *release_fd_cb;
+  int *release_fd;
+
+  grpc_closure read_closure;
+  grpc_closure write_closure;
+
+  char *peer_string;
+} grpc_tcp;
+
+static void tcp_handle_read(grpc_exec_ctx *exec_ctx, void *arg /* grpc_tcp */,
+                            bool success);
+static void tcp_handle_write(grpc_exec_ctx *exec_ctx, void *arg /* grpc_tcp */,
+                             bool success);
+
+static void tcp_shutdown(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  grpc_fd_shutdown(exec_ctx, tcp->em_fd);
+}
+
+static void tcp_free(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
+  grpc_fd_orphan(exec_ctx, tcp->em_fd, tcp->release_fd_cb, tcp->release_fd,
+                 "tcp_unref_orphan");
+  gpr_slice_buffer_destroy(&tcp->last_read_buffer);
+  gpr_free(tcp->peer_string);
+  gpr_free(tcp);
+}
+
+/*#define GRPC_TCP_REFCOUNT_DEBUG*/
+#ifdef GRPC_TCP_REFCOUNT_DEBUG
+#define TCP_UNREF(cl, tcp, reason) \
+  tcp_unref((cl), (tcp), (reason), __FILE__, __LINE__)
+#define TCP_REF(tcp, reason) tcp_ref((tcp), (reason), __FILE__, __LINE__)
+static void tcp_unref(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp,
+                      const char *reason, const char *file, int line) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "TCP unref %p : %s %d -> %d", tcp,
+          reason, tcp->refcount.count, tcp->refcount.count - 1);
+  if (gpr_unref(&tcp->refcount)) {
+    tcp_free(exec_ctx, tcp);
+  }
+}
+
+static void tcp_ref(grpc_tcp *tcp, const char *reason, const char *file,
+                    int line) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "TCP   ref %p : %s %d -> %d", tcp,
+          reason, tcp->refcount.count, tcp->refcount.count + 1);
+  gpr_ref(&tcp->refcount);
+}
+#else
+#define TCP_UNREF(cl, tcp, reason) tcp_unref((cl), (tcp))
+#define TCP_REF(tcp, reason) tcp_ref((tcp))
+static void tcp_unref(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
+  if (gpr_unref(&tcp->refcount)) {
+    tcp_free(exec_ctx, tcp);
+  }
+}
+
+static void tcp_ref(grpc_tcp *tcp) { gpr_ref(&tcp->refcount); }
+#endif
+
+static void tcp_destroy(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  TCP_UNREF(exec_ctx, tcp, "destroy");
+}
+
+static void call_read_cb(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp, int success) {
+  grpc_closure *cb = tcp->read_cb;
+
+  if (grpc_tcp_trace) {
+    size_t i;
+    gpr_log(GPR_DEBUG, "read: success=%d", success);
+    for (i = 0; i < tcp->incoming_buffer->count; i++) {
+      char *dump = gpr_dump_slice(tcp->incoming_buffer->slices[i],
+                                  GPR_DUMP_HEX | GPR_DUMP_ASCII);
+      gpr_log(GPR_DEBUG, "READ %p: %s", tcp, dump);
+      gpr_free(dump);
+    }
+  }
+
+  tcp->read_cb = NULL;
+  tcp->incoming_buffer = NULL;
+  cb->cb(exec_ctx, cb->cb_arg, success);
+}
+
+#define MAX_READ_IOVEC 4
+static void tcp_continue_read(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
+  struct msghdr msg;
+  struct iovec iov[MAX_READ_IOVEC];
+  ssize_t read_bytes;
+  size_t i;
+
+  GPR_ASSERT(!tcp->finished_edge);
+  GPR_ASSERT(tcp->iov_size <= MAX_READ_IOVEC);
+  GPR_ASSERT(tcp->incoming_buffer->count <= MAX_READ_IOVEC);
+  GPR_TIMER_BEGIN("tcp_continue_read", 0);
+
+  while (tcp->incoming_buffer->count < (size_t)tcp->iov_size) {
+    gpr_slice_buffer_add_indexed(tcp->incoming_buffer,
+                                 gpr_slice_malloc(tcp->slice_size));
+  }
+  for (i = 0; i < tcp->incoming_buffer->count; i++) {
+    iov[i].iov_base = GPR_SLICE_START_PTR(tcp->incoming_buffer->slices[i]);
+    iov[i].iov_len = GPR_SLICE_LENGTH(tcp->incoming_buffer->slices[i]);
+  }
+
+  msg.msg_name = NULL;
+  msg.msg_namelen = 0;
+  msg.msg_iov = iov;
+  msg.msg_iovlen = tcp->iov_size;
+  msg.msg_control = NULL;
+  msg.msg_controllen = 0;
+  msg.msg_flags = 0;
+
+  GPR_TIMER_BEGIN("recvmsg", 1);
+  do {
+    read_bytes = recvmsg(tcp->fd, &msg, 0);
+  } while (read_bytes < 0 && errno == EINTR);
+  GPR_TIMER_END("recvmsg", 0);
+
+  if (read_bytes < 0) {
+    /* NB: After calling call_read_cb a parallel call of the read handler may
+     * be running. */
+    if (errno == EAGAIN) {
+      if (tcp->iov_size > 1) {
+        tcp->iov_size /= 2;
+      }
+      /* We've consumed the edge, request a new one */
+      grpc_fd_notify_on_read(exec_ctx, tcp->em_fd, &tcp->read_closure);
+    } else {
+      /* TODO(klempner): Log interesting errors */
+      gpr_slice_buffer_reset_and_unref(tcp->incoming_buffer);
+      call_read_cb(exec_ctx, tcp, 0);
+      TCP_UNREF(exec_ctx, tcp, "read");
+    }
+  } else if (read_bytes == 0) {
+    /* 0 read size ==> end of stream */
+    gpr_slice_buffer_reset_and_unref(tcp->incoming_buffer);
+    call_read_cb(exec_ctx, tcp, 0);
+    TCP_UNREF(exec_ctx, tcp, "read");
+  } else {
+    GPR_ASSERT((size_t)read_bytes <= tcp->incoming_buffer->length);
+    if ((size_t)read_bytes < tcp->incoming_buffer->length) {
+      gpr_slice_buffer_trim_end(
+          tcp->incoming_buffer,
+          tcp->incoming_buffer->length - (size_t)read_bytes,
+          &tcp->last_read_buffer);
+    } else if (tcp->iov_size < MAX_READ_IOVEC) {
+      ++tcp->iov_size;
+    }
+    GPR_ASSERT((size_t)read_bytes == tcp->incoming_buffer->length);
+    call_read_cb(exec_ctx, tcp, 1);
+    TCP_UNREF(exec_ctx, tcp, "read");
+  }
+
+  GPR_TIMER_END("tcp_continue_read", 0);
+}
+
+static void tcp_handle_read(grpc_exec_ctx *exec_ctx, void *arg /* grpc_tcp */,
+                            bool success) {
+  grpc_tcp *tcp = (grpc_tcp *)arg;
+  GPR_ASSERT(!tcp->finished_edge);
+
+  if (!success) {
+    gpr_slice_buffer_reset_and_unref(tcp->incoming_buffer);
+    call_read_cb(exec_ctx, tcp, 0);
+    TCP_UNREF(exec_ctx, tcp, "read");
+  } else {
+    tcp_continue_read(exec_ctx, tcp);
+  }
+}
+
+static void tcp_read(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                     gpr_slice_buffer *incoming_buffer, grpc_closure *cb) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  GPR_ASSERT(tcp->read_cb == NULL);
+  tcp->read_cb = cb;
+  tcp->incoming_buffer = incoming_buffer;
+  gpr_slice_buffer_reset_and_unref(incoming_buffer);
+  gpr_slice_buffer_swap(incoming_buffer, &tcp->last_read_buffer);
+  TCP_REF(tcp, "read");
+  if (tcp->finished_edge) {
+    tcp->finished_edge = 0;
+    grpc_fd_notify_on_read(exec_ctx, tcp->em_fd, &tcp->read_closure);
+  } else {
+    grpc_exec_ctx_enqueue(exec_ctx, &tcp->read_closure, true, NULL);
+  }
+}
+
+typedef enum { FLUSH_DONE, FLUSH_PENDING, FLUSH_ERROR } flush_result;
+
+#define MAX_WRITE_IOVEC 16
+static flush_result tcp_flush(grpc_tcp *tcp) {
+  struct msghdr msg;
+  struct iovec iov[MAX_WRITE_IOVEC];
+  msg_iovlen_type iov_size;
+  ssize_t sent_length;
+  size_t sending_length;
+  size_t trailing;
+  size_t unwind_slice_idx;
+  size_t unwind_byte_idx;
+
+  for (;;) {
+    sending_length = 0;
+    unwind_slice_idx = tcp->outgoing_slice_idx;
+    unwind_byte_idx = tcp->outgoing_byte_idx;
+    for (iov_size = 0; tcp->outgoing_slice_idx != tcp->outgoing_buffer->count &&
+                       iov_size != MAX_WRITE_IOVEC;
+         iov_size++) {
+      iov[iov_size].iov_base =
+          GPR_SLICE_START_PTR(
+              tcp->outgoing_buffer->slices[tcp->outgoing_slice_idx]) +
+          tcp->outgoing_byte_idx;
+      iov[iov_size].iov_len =
+          GPR_SLICE_LENGTH(
+              tcp->outgoing_buffer->slices[tcp->outgoing_slice_idx]) -
+          tcp->outgoing_byte_idx;
+      sending_length += iov[iov_size].iov_len;
+      tcp->outgoing_slice_idx++;
+      tcp->outgoing_byte_idx = 0;
+    }
+    GPR_ASSERT(iov_size > 0);
+
+    msg.msg_name = NULL;
+    msg.msg_namelen = 0;
+    msg.msg_iov = iov;
+    msg.msg_iovlen = iov_size;
+    msg.msg_control = NULL;
+    msg.msg_controllen = 0;
+    msg.msg_flags = 0;
+
+    GPR_TIMER_BEGIN("sendmsg", 1);
+    do {
+      /* TODO(klempner): Cork if this is a partial write */
+      sent_length = sendmsg(tcp->fd, &msg, SENDMSG_FLAGS);
+    } while (sent_length < 0 && errno == EINTR);
+    GPR_TIMER_END("sendmsg", 0);
+
+    if (sent_length < 0) {
+      if (errno == EAGAIN) {
+        tcp->outgoing_slice_idx = unwind_slice_idx;
+        tcp->outgoing_byte_idx = unwind_byte_idx;
+        return FLUSH_PENDING;
+      } else {
+        /* TODO(klempner): Log some of these */
+        return FLUSH_ERROR;
+      }
+    }
+
+    GPR_ASSERT(tcp->outgoing_byte_idx == 0);
+    trailing = sending_length - (size_t)sent_length;
+    while (trailing > 0) {
+      size_t slice_length;
+
+      tcp->outgoing_slice_idx--;
+      slice_length = GPR_SLICE_LENGTH(
+          tcp->outgoing_buffer->slices[tcp->outgoing_slice_idx]);
+      if (slice_length > trailing) {
+        tcp->outgoing_byte_idx = slice_length - trailing;
+        break;
+      } else {
+        trailing -= slice_length;
+      }
+    }
+
+    if (tcp->outgoing_slice_idx == tcp->outgoing_buffer->count) {
+      return FLUSH_DONE;
+    }
+  };
+}
+
+static void tcp_handle_write(grpc_exec_ctx *exec_ctx, void *arg /* grpc_tcp */,
+                             bool success) {
+  grpc_tcp *tcp = (grpc_tcp *)arg;
+  flush_result status;
+  grpc_closure *cb;
+
+  if (!success) {
+    cb = tcp->write_cb;
+    tcp->write_cb = NULL;
+    cb->cb(exec_ctx, cb->cb_arg, 0);
+    TCP_UNREF(exec_ctx, tcp, "write");
+    return;
+  }
+
+  status = tcp_flush(tcp);
+  if (status == FLUSH_PENDING) {
+    grpc_fd_notify_on_write(exec_ctx, tcp->em_fd, &tcp->write_closure);
+  } else {
+    cb = tcp->write_cb;
+    tcp->write_cb = NULL;
+    GPR_TIMER_BEGIN("tcp_handle_write.cb", 0);
+    cb->cb(exec_ctx, cb->cb_arg, status == FLUSH_DONE);
+    GPR_TIMER_END("tcp_handle_write.cb", 0);
+    TCP_UNREF(exec_ctx, tcp, "write");
+  }
+}
+
+static void tcp_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                      gpr_slice_buffer *buf, grpc_closure *cb) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  flush_result status;
+
+  if (grpc_tcp_trace) {
+    size_t i;
+
+    for (i = 0; i < buf->count; i++) {
+      char *data =
+          gpr_dump_slice(buf->slices[i], GPR_DUMP_HEX | GPR_DUMP_ASCII);
+      gpr_log(GPR_DEBUG, "WRITE %p: %s", tcp, data);
+      gpr_free(data);
+    }
+  }
+
+  GPR_TIMER_BEGIN("tcp_write", 0);
+  GPR_ASSERT(tcp->write_cb == NULL);
+
+  if (buf->length == 0) {
+    GPR_TIMER_END("tcp_write", 0);
+    grpc_exec_ctx_enqueue(exec_ctx, cb, true, NULL);
+    return;
+  }
+  tcp->outgoing_buffer = buf;
+  tcp->outgoing_slice_idx = 0;
+  tcp->outgoing_byte_idx = 0;
+
+  status = tcp_flush(tcp);
+  if (status == FLUSH_PENDING) {
+    TCP_REF(tcp, "write");
+    tcp->write_cb = cb;
+    grpc_fd_notify_on_write(exec_ctx, tcp->em_fd, &tcp->write_closure);
+  } else {
+    grpc_exec_ctx_enqueue(exec_ctx, cb, status == FLUSH_DONE, NULL);
+  }
+
+  GPR_TIMER_END("tcp_write", 0);
+}
+
+static void tcp_add_to_pollset(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                               grpc_pollset *pollset) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  grpc_pollset_add_fd(exec_ctx, pollset, tcp->em_fd);
+}
+
+static void tcp_add_to_pollset_set(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                                   grpc_pollset_set *pollset_set) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  grpc_pollset_set_add_fd(exec_ctx, pollset_set, tcp->em_fd);
+}
+
+static char *tcp_get_peer(grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  return gpr_strdup(tcp->peer_string);
+}
+
+static const grpc_endpoint_vtable vtable = {
+    tcp_read,     tcp_write,   tcp_add_to_pollset, tcp_add_to_pollset_set,
+    tcp_shutdown, tcp_destroy, tcp_get_peer};
+
+grpc_endpoint *grpc_tcp_create(grpc_fd *em_fd, size_t slice_size,
+                               const char *peer_string) {
+  grpc_tcp *tcp = (grpc_tcp *)gpr_malloc(sizeof(grpc_tcp));
+  tcp->base.vtable = &vtable;
+  tcp->peer_string = gpr_strdup(peer_string);
+  tcp->fd = grpc_fd_wrapped_fd(em_fd);
+  tcp->read_cb = NULL;
+  tcp->write_cb = NULL;
+  tcp->release_fd_cb = NULL;
+  tcp->release_fd = NULL;
+  tcp->incoming_buffer = NULL;
+  tcp->slice_size = slice_size;
+  tcp->iov_size = 1;
+  tcp->finished_edge = 1;
+  /* paired with unref in grpc_tcp_destroy */
+  gpr_ref_init(&tcp->refcount, 1);
+  tcp->em_fd = em_fd;
+  tcp->read_closure.cb = tcp_handle_read;
+  tcp->read_closure.cb_arg = tcp;
+  tcp->write_closure.cb = tcp_handle_write;
+  tcp->write_closure.cb_arg = tcp;
+  gpr_slice_buffer_init(&tcp->last_read_buffer);
+
+  return &tcp->base;
+}
+
+int grpc_tcp_fd(grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  GPR_ASSERT(ep->vtable == &vtable);
+  return grpc_fd_wrapped_fd(tcp->em_fd);
+}
+
+void grpc_tcp_destroy_and_release_fd(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                                     int *fd, grpc_closure *done) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  GPR_ASSERT(ep->vtable == &vtable);
+  tcp->release_fd = fd;
+  tcp->release_fd_cb = done;
+  TCP_UNREF(exec_ctx, tcp, "destroy");
+}
+
+#endif
diff --git a/src/core/lib/iomgr/tcp_posix.h b/src/core/lib/iomgr/tcp_posix.h
new file mode 100644
index 0000000000..c9b70aaa33
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_posix.h
@@ -0,0 +1,71 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_TCP_POSIX_H
+#define GRPC_CORE_LIB_IOMGR_TCP_POSIX_H
+/*
+   Low level TCP "bottom half" implementation, for use by transports built on
+   top of a TCP connection.
+
+   Note that this file does not (yet) include APIs for creating the socket in
+   the first place.
+
+   All calls passing slice transfer ownership of a slice refcount unless
+   otherwise specified.
+*/
+
+#include "src/core/lib/iomgr/endpoint.h"
+#include "src/core/lib/iomgr/ev_posix.h"
+
+#define GRPC_TCP_DEFAULT_READ_SLICE_SIZE 8192
+
+extern int grpc_tcp_trace;
+
+/* Create a tcp endpoint given a file desciptor and a read slice size.
+   Takes ownership of fd. */
+grpc_endpoint *grpc_tcp_create(grpc_fd *fd, size_t read_slice_size,
+                               const char *peer_string);
+
+/* Return the tcp endpoint's fd, or -1 if this is not available. Does not
+   release the fd.
+   Requires: ep must be a tcp endpoint.
+ */
+int grpc_tcp_fd(grpc_endpoint *ep);
+
+/* Destroy the tcp endpoint without closing its fd. *fd will be set and done
+ * will be called when the endpoint is destroyed.
+ * Requires: ep must be a tcp endpoint and fd must not be NULL. */
+void grpc_tcp_destroy_and_release_fd(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                                     int *fd, grpc_closure *done);
+
+#endif /* GRPC_CORE_LIB_IOMGR_TCP_POSIX_H */
diff --git a/src/core/lib/iomgr/tcp_server.h b/src/core/lib/iomgr/tcp_server.h
new file mode 100644
index 0000000000..81edb61997
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_server.h
@@ -0,0 +1,103 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_TCP_SERVER_H
+#define GRPC_CORE_LIB_IOMGR_TCP_SERVER_H
+
+#include "src/core/lib/iomgr/closure.h"
+#include "src/core/lib/iomgr/endpoint.h"
+
+/* Forward decl of grpc_tcp_server */
+typedef struct grpc_tcp_server grpc_tcp_server;
+
+typedef struct grpc_tcp_server_acceptor {
+  /* grpc_tcp_server_cb functions share a ref on from_server that is valid
+     until the function returns. */
+  grpc_tcp_server *from_server;
+  /* Indices that may be passed to grpc_tcp_server_port_fd(). */
+  unsigned port_index;
+  unsigned fd_index;
+} grpc_tcp_server_acceptor;
+
+/* Called for newly connected TCP connections. */
+typedef void (*grpc_tcp_server_cb)(grpc_exec_ctx *exec_ctx, void *arg,
+                                   grpc_endpoint *ep,
+                                   grpc_tcp_server_acceptor *acceptor);
+
+/* Create a server, initially not bound to any ports. The caller owns one ref.
+   If shutdown_complete is not NULL, it will be used by
+   grpc_tcp_server_unref() when the ref count reaches zero. */
+grpc_tcp_server *grpc_tcp_server_create(grpc_closure *shutdown_complete);
+
+/* Start listening to bound ports */
+void grpc_tcp_server_start(grpc_exec_ctx *exec_ctx, grpc_tcp_server *server,
+                           grpc_pollset **pollsets, size_t pollset_count,
+                           grpc_tcp_server_cb on_accept_cb, void *cb_arg);
+
+/* Add a port to the server, returning the newly allocated port on success, or
+   -1 on failure.
+
+   The :: and 0.0.0.0 wildcard addresses are treated identically, accepting
+   both IPv4 and IPv6 connections, but :: is the preferred style.  This usually
+   creates one socket, but possibly two on systems which support IPv6,
+   but not dualstack sockets. */
+/* TODO(ctiller): deprecate this, and make grpc_tcp_server_add_ports to handle
+                  all of the multiple socket port matching logic in one place */
+int grpc_tcp_server_add_port(grpc_tcp_server *s, const void *addr,
+                             size_t addr_len);
+
+/* Number of fds at the given port_index, or 0 if port_index is out of
+   bounds. */
+unsigned grpc_tcp_server_port_fd_count(grpc_tcp_server *s, unsigned port_index);
+
+/* Returns the file descriptor of the Mth (fd_index) listening socket of the Nth
+   (port_index) call to add_port() on this server, or -1 if the indices are out
+   of bounds. The file descriptor remains owned by the server, and will be
+   cleaned up when the ref count reaches zero. */
+int grpc_tcp_server_port_fd(grpc_tcp_server *s, unsigned port_index,
+                            unsigned fd_index);
+
+/* Ref s and return s. */
+grpc_tcp_server *grpc_tcp_server_ref(grpc_tcp_server *s);
+
+/* shutdown_starting is called when ref count has reached zero and the server is
+   about to be destroyed. The server will be deleted after it returns. Calling
+   grpc_tcp_server_ref() from it has no effect. */
+void grpc_tcp_server_shutdown_starting_add(grpc_tcp_server *s,
+                                           grpc_closure *shutdown_starting);
+
+/* If the refcount drops to zero, delete s, and call (exec_ctx==NULL) or enqueue
+   a call (exec_ctx!=NULL) to shutdown_complete. */
+void grpc_tcp_server_unref(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s);
+
+#endif /* GRPC_CORE_LIB_IOMGR_TCP_SERVER_H */
diff --git a/src/core/lib/iomgr/tcp_server_posix.c b/src/core/lib/iomgr/tcp_server_posix.c
new file mode 100644
index 0000000000..313ec226c9
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_server_posix.c
@@ -0,0 +1,606 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/* FIXME: "posix" files shouldn't be depending on _GNU_SOURCE */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/tcp_server.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/time.h>
+#include "src/core/lib/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+#include "src/core/lib/iomgr/tcp_posix.h"
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+#include "src/core/lib/support/string.h"
+
+#define MIN_SAFE_ACCEPT_QUEUE_SIZE 100
+
+static gpr_once s_init_max_accept_queue_size;
+static int s_max_accept_queue_size;
+
+/* one listening port */
+typedef struct grpc_tcp_listener grpc_tcp_listener;
+struct grpc_tcp_listener {
+  int fd;
+  grpc_fd *emfd;
+  grpc_tcp_server *server;
+  union {
+    uint8_t untyped[GRPC_MAX_SOCKADDR_SIZE];
+    struct sockaddr sockaddr;
+  } addr;
+  size_t addr_len;
+  int port;
+  unsigned port_index;
+  unsigned fd_index;
+  grpc_closure read_closure;
+  grpc_closure destroyed_closure;
+  struct grpc_tcp_listener *next;
+  /* When we add a listener, more than one can be created, mainly because of
+     IPv6. A sibling will still be in the normal list, but will be flagged
+     as such. Any action, such as ref or unref, will affect all of the
+     siblings in the list. */
+  struct grpc_tcp_listener *sibling;
+  int is_sibling;
+};
+
+/* the overall server */
+struct grpc_tcp_server {
+  gpr_refcount refs;
+  /* Called whenever accept() succeeds on a server port. */
+  grpc_tcp_server_cb on_accept_cb;
+  void *on_accept_cb_arg;
+
+  gpr_mu mu;
+
+  /* active port count: how many ports are actually still listening */
+  size_t active_ports;
+  /* destroyed port count: how many ports are completely destroyed */
+  size_t destroyed_ports;
+
+  /* is this server shutting down? (boolean) */
+  int shutdown;
+
+  /* linked list of server ports */
+  grpc_tcp_listener *head;
+  grpc_tcp_listener *tail;
+  unsigned nports;
+
+  /* List of closures passed to shutdown_starting_add(). */
+  grpc_closure_list shutdown_starting;
+
+  /* shutdown callback */
+  grpc_closure *shutdown_complete;
+
+  /* all pollsets interested in new connections */
+  grpc_pollset **pollsets;
+  /* number of pollsets in the pollsets array */
+  size_t pollset_count;
+};
+
+grpc_tcp_server *grpc_tcp_server_create(grpc_closure *shutdown_complete) {
+  grpc_tcp_server *s = gpr_malloc(sizeof(grpc_tcp_server));
+  gpr_ref_init(&s->refs, 1);
+  gpr_mu_init(&s->mu);
+  s->active_ports = 0;
+  s->destroyed_ports = 0;
+  s->shutdown = 0;
+  s->shutdown_starting.head = NULL;
+  s->shutdown_starting.tail = NULL;
+  s->shutdown_complete = shutdown_complete;
+  s->on_accept_cb = NULL;
+  s->on_accept_cb_arg = NULL;
+  s->head = NULL;
+  s->tail = NULL;
+  s->nports = 0;
+  return s;
+}
+
+static void finish_shutdown(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
+  if (s->shutdown_complete != NULL) {
+    grpc_exec_ctx_enqueue(exec_ctx, s->shutdown_complete, true, NULL);
+  }
+
+  gpr_mu_destroy(&s->mu);
+
+  while (s->head) {
+    grpc_tcp_listener *sp = s->head;
+    s->head = sp->next;
+    gpr_free(sp);
+  }
+
+  gpr_free(s);
+}
+
+static void destroyed_port(grpc_exec_ctx *exec_ctx, void *server,
+                           bool success) {
+  grpc_tcp_server *s = server;
+  gpr_mu_lock(&s->mu);
+  s->destroyed_ports++;
+  if (s->destroyed_ports == s->nports) {
+    gpr_mu_unlock(&s->mu);
+    finish_shutdown(exec_ctx, s);
+  } else {
+    GPR_ASSERT(s->destroyed_ports < s->nports);
+    gpr_mu_unlock(&s->mu);
+  }
+}
+
+/* called when all listening endpoints have been shutdown, so no further
+   events will be received on them - at this point it's safe to destroy
+   things */
+static void deactivated_all_ports(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
+  /* delete ALL the things */
+  gpr_mu_lock(&s->mu);
+
+  if (!s->shutdown) {
+    gpr_mu_unlock(&s->mu);
+    return;
+  }
+
+  if (s->head) {
+    grpc_tcp_listener *sp;
+    for (sp = s->head; sp; sp = sp->next) {
+      grpc_unlink_if_unix_domain_socket(&sp->addr.sockaddr);
+      sp->destroyed_closure.cb = destroyed_port;
+      sp->destroyed_closure.cb_arg = s;
+      grpc_fd_orphan(exec_ctx, sp->emfd, &sp->destroyed_closure, NULL,
+                     "tcp_listener_shutdown");
+    }
+    gpr_mu_unlock(&s->mu);
+  } else {
+    gpr_mu_unlock(&s->mu);
+    finish_shutdown(exec_ctx, s);
+  }
+}
+
+static void tcp_server_destroy(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
+  gpr_mu_lock(&s->mu);
+
+  GPR_ASSERT(!s->shutdown);
+  s->shutdown = 1;
+
+  /* shutdown all fd's */
+  if (s->active_ports) {
+    grpc_tcp_listener *sp;
+    for (sp = s->head; sp; sp = sp->next) {
+      grpc_fd_shutdown(exec_ctx, sp->emfd);
+    }
+    gpr_mu_unlock(&s->mu);
+  } else {
+    gpr_mu_unlock(&s->mu);
+    deactivated_all_ports(exec_ctx, s);
+  }
+}
+
+/* get max listen queue size on linux */
+static void init_max_accept_queue_size(void) {
+  int n = SOMAXCONN;
+  char buf[64];
+  FILE *fp = fopen("/proc/sys/net/core/somaxconn", "r");
+  if (fp == NULL) {
+    /* 2.4 kernel. */
+    s_max_accept_queue_size = SOMAXCONN;
+    return;
+  }
+  if (fgets(buf, sizeof buf, fp)) {
+    char *end;
+    long i = strtol(buf, &end, 10);
+    if (i > 0 && i <= INT_MAX && end && *end == 0) {
+      n = (int)i;
+    }
+  }
+  fclose(fp);
+  s_max_accept_queue_size = n;
+
+  if (s_max_accept_queue_size < MIN_SAFE_ACCEPT_QUEUE_SIZE) {
+    gpr_log(GPR_INFO,
+            "Suspiciously small accept queue (%d) will probably lead to "
+            "connection drops",
+            s_max_accept_queue_size);
+  }
+}
+
+static int get_max_accept_queue_size(void) {
+  gpr_once_init(&s_init_max_accept_queue_size, init_max_accept_queue_size);
+  return s_max_accept_queue_size;
+}
+
+/* Prepare a recently-created socket for listening. */
+static int prepare_socket(int fd, const struct sockaddr *addr,
+                          size_t addr_len) {
+  struct sockaddr_storage sockname_temp;
+  socklen_t sockname_len;
+
+  if (fd < 0) {
+    goto error;
+  }
+
+  if (!grpc_set_socket_nonblocking(fd, 1) || !grpc_set_socket_cloexec(fd, 1) ||
+      (!grpc_is_unix_socket(addr) && (!grpc_set_socket_low_latency(fd, 1) ||
+                                      !grpc_set_socket_reuse_addr(fd, 1))) ||
+      !grpc_set_socket_no_sigpipe_if_possible(fd)) {
+    gpr_log(GPR_ERROR, "Unable to configure socket %d: %s", fd,
+            strerror(errno));
+    goto error;
+  }
+
+  GPR_ASSERT(addr_len < ~(socklen_t)0);
+  if (bind(fd, addr, (socklen_t)addr_len) < 0) {
+    char *addr_str;
+    grpc_sockaddr_to_string(&addr_str, addr, 0);
+    gpr_log(GPR_ERROR, "bind addr=%s: %s", addr_str, strerror(errno));
+    gpr_free(addr_str);
+    goto error;
+  }
+
+  if (listen(fd, get_max_accept_queue_size()) < 0) {
+    gpr_log(GPR_ERROR, "listen: %s", strerror(errno));
+    goto error;
+  }
+
+  sockname_len = sizeof(sockname_temp);
+  if (getsockname(fd, (struct sockaddr *)&sockname_temp, &sockname_len) < 0) {
+    goto error;
+  }
+
+  return grpc_sockaddr_get_port((struct sockaddr *)&sockname_temp);
+
+error:
+  if (fd >= 0) {
+    close(fd);
+  }
+  return -1;
+}
+
+/* event manager callback when reads are ready */
+static void on_read(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
+  grpc_tcp_listener *sp = arg;
+  grpc_tcp_server_acceptor acceptor = {sp->server, sp->port_index,
+                                       sp->fd_index};
+  grpc_fd *fdobj;
+  size_t i;
+
+  if (!success) {
+    goto error;
+  }
+
+  /* loop until accept4 returns EAGAIN, and then re-arm notification */
+  for (;;) {
+    struct sockaddr_storage addr;
+    socklen_t addrlen = sizeof(addr);
+    char *addr_str;
+    char *name;
+    /* Note: If we ever decide to return this address to the user, remember to
+       strip off the ::ffff:0.0.0.0/96 prefix first. */
+    int fd = grpc_accept4(sp->fd, (struct sockaddr *)&addr, &addrlen, 1, 1);
+    if (fd < 0) {
+      switch (errno) {
+        case EINTR:
+          continue;
+        case EAGAIN:
+          grpc_fd_notify_on_read(exec_ctx, sp->emfd, &sp->read_closure);
+          return;
+        default:
+          gpr_log(GPR_ERROR, "Failed accept4: %s", strerror(errno));
+          goto error;
+      }
+    }
+
+    grpc_set_socket_no_sigpipe_if_possible(fd);
+
+    addr_str = grpc_sockaddr_to_uri((struct sockaddr *)&addr);
+    gpr_asprintf(&name, "tcp-server-connection:%s", addr_str);
+
+    if (grpc_tcp_trace) {
+      gpr_log(GPR_DEBUG, "SERVER_CONNECT: incoming connection: %s", addr_str);
+    }
+
+    fdobj = grpc_fd_create(fd, name);
+    /* TODO(ctiller): revise this when we have server-side sharding
+       of channels -- we certainly should not be automatically adding every
+       incoming channel to every pollset owned by the server */
+    for (i = 0; i < sp->server->pollset_count; i++) {
+      grpc_pollset_add_fd(exec_ctx, sp->server->pollsets[i], fdobj);
+    }
+    sp->server->on_accept_cb(
+        exec_ctx, sp->server->on_accept_cb_arg,
+        grpc_tcp_create(fdobj, GRPC_TCP_DEFAULT_READ_SLICE_SIZE, addr_str),
+        &acceptor);
+
+    gpr_free(name);
+    gpr_free(addr_str);
+  }
+
+  GPR_UNREACHABLE_CODE(return );
+
+error:
+  gpr_mu_lock(&sp->server->mu);
+  if (0 == --sp->server->active_ports) {
+    gpr_mu_unlock(&sp->server->mu);
+    deactivated_all_ports(exec_ctx, sp->server);
+  } else {
+    gpr_mu_unlock(&sp->server->mu);
+  }
+}
+
+static grpc_tcp_listener *add_socket_to_server(grpc_tcp_server *s, int fd,
+                                               const struct sockaddr *addr,
+                                               size_t addr_len,
+                                               unsigned port_index,
+                                               unsigned fd_index) {
+  grpc_tcp_listener *sp = NULL;
+  int port;
+  char *addr_str;
+  char *name;
+
+  port = prepare_socket(fd, addr, addr_len);
+  if (port >= 0) {
+    grpc_sockaddr_to_string(&addr_str, (struct sockaddr *)&addr, 1);
+    gpr_asprintf(&name, "tcp-server-listener:%s", addr_str);
+    gpr_mu_lock(&s->mu);
+    s->nports++;
+    GPR_ASSERT(!s->on_accept_cb && "must add ports before starting server");
+    sp = gpr_malloc(sizeof(grpc_tcp_listener));
+    sp->next = NULL;
+    if (s->head == NULL) {
+      s->head = sp;
+    } else {
+      s->tail->next = sp;
+    }
+    s->tail = sp;
+    sp->server = s;
+    sp->fd = fd;
+    sp->emfd = grpc_fd_create(fd, name);
+    memcpy(sp->addr.untyped, addr, addr_len);
+    sp->addr_len = addr_len;
+    sp->port = port;
+    sp->port_index = port_index;
+    sp->fd_index = fd_index;
+    sp->is_sibling = 0;
+    sp->sibling = NULL;
+    GPR_ASSERT(sp->emfd);
+    gpr_mu_unlock(&s->mu);
+    gpr_free(addr_str);
+    gpr_free(name);
+  }
+
+  return sp;
+}
+
+int grpc_tcp_server_add_port(grpc_tcp_server *s, const void *addr,
+                             size_t addr_len) {
+  grpc_tcp_listener *sp;
+  grpc_tcp_listener *sp2 = NULL;
+  int fd;
+  grpc_dualstack_mode dsmode;
+  struct sockaddr_in6 addr6_v4mapped;
+  struct sockaddr_in wild4;
+  struct sockaddr_in6 wild6;
+  struct sockaddr_in addr4_copy;
+  struct sockaddr *allocated_addr = NULL;
+  struct sockaddr_storage sockname_temp;
+  socklen_t sockname_len;
+  int port;
+  unsigned port_index = 0;
+  unsigned fd_index = 0;
+  if (s->tail != NULL) {
+    port_index = s->tail->port_index + 1;
+  }
+  grpc_unlink_if_unix_domain_socket((struct sockaddr *)addr);
+
+  /* Check if this is a wildcard port, and if so, try to keep the port the same
+     as some previously created listener. */
+  if (grpc_sockaddr_get_port(addr) == 0) {
+    for (sp = s->head; sp; sp = sp->next) {
+      sockname_len = sizeof(sockname_temp);
+      if (0 == getsockname(sp->fd, (struct sockaddr *)&sockname_temp,
+                           &sockname_len)) {
+        port = grpc_sockaddr_get_port((struct sockaddr *)&sockname_temp);
+        if (port > 0) {
+          allocated_addr = malloc(addr_len);
+          memcpy(allocated_addr, addr, addr_len);
+          grpc_sockaddr_set_port(allocated_addr, port);
+          addr = allocated_addr;
+          break;
+        }
+      }
+    }
+  }
+
+  sp = NULL;
+
+  if (grpc_sockaddr_to_v4mapped(addr, &addr6_v4mapped)) {
+    addr = (const struct sockaddr *)&addr6_v4mapped;
+    addr_len = sizeof(addr6_v4mapped);
+  }
+
+  /* Treat :: or 0.0.0.0 as a family-agnostic wildcard. */
+  if (grpc_sockaddr_is_wildcard(addr, &port)) {
+    grpc_sockaddr_make_wildcards(port, &wild4, &wild6);
+
+    /* Try listening on IPv6 first. */
+    addr = (struct sockaddr *)&wild6;
+    addr_len = sizeof(wild6);
+    fd = grpc_create_dualstack_socket(addr, SOCK_STREAM, 0, &dsmode);
+    sp = add_socket_to_server(s, fd, addr, addr_len, port_index, fd_index);
+    if (fd >= 0 && dsmode == GRPC_DSMODE_DUALSTACK) {
+      goto done;
+    }
+    if (sp != NULL) {
+      ++fd_index;
+    }
+    /* If we didn't get a dualstack socket, also listen on 0.0.0.0. */
+    if (port == 0 && sp != NULL) {
+      grpc_sockaddr_set_port((struct sockaddr *)&wild4, sp->port);
+    }
+    addr = (struct sockaddr *)&wild4;
+    addr_len = sizeof(wild4);
+  }
+
+  fd = grpc_create_dualstack_socket(addr, SOCK_STREAM, 0, &dsmode);
+  if (fd < 0) {
+    gpr_log(GPR_ERROR, "Unable to create socket: %s", strerror(errno));
+  } else {
+    if (dsmode == GRPC_DSMODE_IPV4 &&
+        grpc_sockaddr_is_v4mapped(addr, &addr4_copy)) {
+      addr = (struct sockaddr *)&addr4_copy;
+      addr_len = sizeof(addr4_copy);
+    }
+    sp2 = sp;
+    sp = add_socket_to_server(s, fd, addr, addr_len, port_index, fd_index);
+    if (sp2 != NULL && sp != NULL) {
+      sp2->sibling = sp;
+      sp->is_sibling = 1;
+    }
+  }
+
+done:
+  gpr_free(allocated_addr);
+  if (sp != NULL) {
+    return sp->port;
+  } else {
+    return -1;
+  }
+}
+
+unsigned grpc_tcp_server_port_fd_count(grpc_tcp_server *s,
+                                       unsigned port_index) {
+  unsigned num_fds = 0;
+  grpc_tcp_listener *sp;
+  for (sp = s->head; sp && port_index != 0; sp = sp->next) {
+    if (!sp->is_sibling) {
+      --port_index;
+    }
+  }
+  for (; sp; sp = sp->sibling, ++num_fds)
+    ;
+  return num_fds;
+}
+
+int grpc_tcp_server_port_fd(grpc_tcp_server *s, unsigned port_index,
+                            unsigned fd_index) {
+  grpc_tcp_listener *sp;
+  for (sp = s->head; sp && port_index != 0; sp = sp->next) {
+    if (!sp->is_sibling) {
+      --port_index;
+    }
+  }
+  for (; sp && fd_index != 0; sp = sp->sibling, --fd_index)
+    ;
+  if (sp) {
+    return sp->fd;
+  } else {
+    return -1;
+  }
+}
+
+void grpc_tcp_server_start(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s,
+                           grpc_pollset **pollsets, size_t pollset_count,
+                           grpc_tcp_server_cb on_accept_cb,
+                           void *on_accept_cb_arg) {
+  size_t i;
+  grpc_tcp_listener *sp;
+  GPR_ASSERT(on_accept_cb);
+  gpr_mu_lock(&s->mu);
+  GPR_ASSERT(!s->on_accept_cb);
+  GPR_ASSERT(s->active_ports == 0);
+  s->on_accept_cb = on_accept_cb;
+  s->on_accept_cb_arg = on_accept_cb_arg;
+  s->pollsets = pollsets;
+  s->pollset_count = pollset_count;
+  for (sp = s->head; sp; sp = sp->next) {
+    for (i = 0; i < pollset_count; i++) {
+      grpc_pollset_add_fd(exec_ctx, pollsets[i], sp->emfd);
+    }
+    sp->read_closure.cb = on_read;
+    sp->read_closure.cb_arg = sp;
+    grpc_fd_notify_on_read(exec_ctx, sp->emfd, &sp->read_closure);
+    s->active_ports++;
+  }
+  gpr_mu_unlock(&s->mu);
+}
+
+grpc_tcp_server *grpc_tcp_server_ref(grpc_tcp_server *s) {
+  gpr_ref(&s->refs);
+  return s;
+}
+
+void grpc_tcp_server_shutdown_starting_add(grpc_tcp_server *s,
+                                           grpc_closure *shutdown_starting) {
+  gpr_mu_lock(&s->mu);
+  grpc_closure_list_add(&s->shutdown_starting, shutdown_starting, 1);
+  gpr_mu_unlock(&s->mu);
+}
+
+void grpc_tcp_server_unref(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
+  if (gpr_unref(&s->refs)) {
+    /* Complete shutdown_starting work before destroying. */
+    grpc_exec_ctx local_exec_ctx = GRPC_EXEC_CTX_INIT;
+    gpr_mu_lock(&s->mu);
+    grpc_exec_ctx_enqueue_list(&local_exec_ctx, &s->shutdown_starting, NULL);
+    gpr_mu_unlock(&s->mu);
+    if (exec_ctx == NULL) {
+      grpc_exec_ctx_flush(&local_exec_ctx);
+      tcp_server_destroy(&local_exec_ctx, s);
+      grpc_exec_ctx_finish(&local_exec_ctx);
+    } else {
+      grpc_exec_ctx_finish(&local_exec_ctx);
+      tcp_server_destroy(exec_ctx, s);
+    }
+  }
+}
+
+#endif
diff --git a/src/core/lib/iomgr/tcp_server_windows.c b/src/core/lib/iomgr/tcp_server_windows.c
new file mode 100644
index 0000000000..3d6a29b2e2
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_server_windows.c
@@ -0,0 +1,557 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include <io.h>
+
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/log_win32.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/time.h>
+
+#include "src/core/lib/iomgr/iocp_windows.h"
+#include "src/core/lib/iomgr/pollset_windows.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+#include "src/core/lib/iomgr/tcp_server.h"
+#include "src/core/lib/iomgr/tcp_windows.h"
+
+#define MIN_SAFE_ACCEPT_QUEUE_SIZE 100
+
+/* one listening port */
+typedef struct grpc_tcp_listener grpc_tcp_listener;
+struct grpc_tcp_listener {
+  /* This seemingly magic number comes from AcceptEx's documentation. each
+     address buffer needs to have at least 16 more bytes at their end. */
+  uint8_t addresses[(sizeof(struct sockaddr_in6) + 16) * 2];
+  /* This will hold the socket for the next accept. */
+  SOCKET new_socket;
+  /* The listener winsocket. */
+  grpc_winsocket *socket;
+  /* The actual TCP port number. */
+  int port;
+  unsigned port_index;
+  grpc_tcp_server *server;
+  /* The cached AcceptEx for that port. */
+  LPFN_ACCEPTEX AcceptEx;
+  int shutting_down;
+  /* closure for socket notification of accept being ready */
+  grpc_closure on_accept;
+  /* linked list */
+  struct grpc_tcp_listener *next;
+};
+
+/* the overall server */
+struct grpc_tcp_server {
+  gpr_refcount refs;
+  /* Called whenever accept() succeeds on a server port. */
+  grpc_tcp_server_cb on_accept_cb;
+  void *on_accept_cb_arg;
+
+  gpr_mu mu;
+
+  /* active port count: how many ports are actually still listening */
+  int active_ports;
+
+  /* linked list of server ports */
+  grpc_tcp_listener *head;
+  grpc_tcp_listener *tail;
+
+  /* List of closures passed to shutdown_starting_add(). */
+  grpc_closure_list shutdown_starting;
+
+  /* shutdown callback */
+  grpc_closure *shutdown_complete;
+};
+
+/* Public function. Allocates the proper data structures to hold a
+   grpc_tcp_server. */
+grpc_tcp_server *grpc_tcp_server_create(grpc_closure *shutdown_complete) {
+  grpc_tcp_server *s = gpr_malloc(sizeof(grpc_tcp_server));
+  gpr_ref_init(&s->refs, 1);
+  gpr_mu_init(&s->mu);
+  s->active_ports = 0;
+  s->on_accept_cb = NULL;
+  s->on_accept_cb_arg = NULL;
+  s->head = NULL;
+  s->tail = NULL;
+  s->shutdown_starting.head = NULL;
+  s->shutdown_starting.tail = NULL;
+  s->shutdown_complete = shutdown_complete;
+  return s;
+}
+
+static void finish_shutdown(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
+  if (s->shutdown_complete != NULL) {
+    grpc_exec_ctx_enqueue(exec_ctx, s->shutdown_complete, true, NULL);
+  }
+
+  /* Now that the accepts have been aborted, we can destroy the sockets.
+     The IOCP won't get notified on these, so we can flag them as already
+     closed by the system. */
+  while (s->head) {
+    grpc_tcp_listener *sp = s->head;
+    s->head = sp->next;
+    sp->next = NULL;
+    grpc_winsocket_destroy(sp->socket);
+    gpr_free(sp);
+  }
+  gpr_free(s);
+}
+
+grpc_tcp_server *grpc_tcp_server_ref(grpc_tcp_server *s) {
+  gpr_ref(&s->refs);
+  return s;
+}
+
+void grpc_tcp_server_shutdown_starting_add(grpc_tcp_server *s,
+                                           grpc_closure *shutdown_starting) {
+  gpr_mu_lock(&s->mu);
+  grpc_closure_list_add(&s->shutdown_starting, shutdown_starting, 1);
+  gpr_mu_unlock(&s->mu);
+}
+
+static void tcp_server_destroy(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
+  int immediately_done = 0;
+  grpc_tcp_listener *sp;
+  gpr_mu_lock(&s->mu);
+
+  /* First, shutdown all fd's. This will queue abortion calls for all
+     of the pending accepts due to the normal operation mechanism. */
+  if (s->active_ports == 0) {
+    immediately_done = 1;
+  }
+  for (sp = s->head; sp; sp = sp->next) {
+    sp->shutting_down = 1;
+    grpc_winsocket_shutdown(sp->socket);
+  }
+  gpr_mu_unlock(&s->mu);
+
+  if (immediately_done) {
+    finish_shutdown(exec_ctx, s);
+  }
+}
+
+void grpc_tcp_server_unref(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
+  if (gpr_unref(&s->refs)) {
+    /* Complete shutdown_starting work before destroying. */
+    grpc_exec_ctx local_exec_ctx = GRPC_EXEC_CTX_INIT;
+    gpr_mu_lock(&s->mu);
+    grpc_exec_ctx_enqueue_list(&local_exec_ctx, &s->shutdown_starting, NULL);
+    gpr_mu_unlock(&s->mu);
+    if (exec_ctx == NULL) {
+      grpc_exec_ctx_flush(&local_exec_ctx);
+      tcp_server_destroy(&local_exec_ctx, s);
+      grpc_exec_ctx_finish(&local_exec_ctx);
+    } else {
+      grpc_exec_ctx_finish(&local_exec_ctx);
+      tcp_server_destroy(exec_ctx, s);
+    }
+  }
+}
+
+/* Prepare (bind) a recently-created socket for listening. */
+static int prepare_socket(SOCKET sock, const struct sockaddr *addr,
+                          size_t addr_len) {
+  struct sockaddr_storage sockname_temp;
+  socklen_t sockname_len;
+
+  if (sock == INVALID_SOCKET) goto error;
+
+  if (!grpc_tcp_prepare_socket(sock)) {
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    gpr_log(GPR_ERROR, "Unable to prepare socket: %s", utf8_message);
+    gpr_free(utf8_message);
+    goto error;
+  }
+
+  if (bind(sock, addr, (int)addr_len) == SOCKET_ERROR) {
+    char *addr_str;
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    grpc_sockaddr_to_string(&addr_str, addr, 0);
+    gpr_log(GPR_ERROR, "bind addr=%s: %s", addr_str, utf8_message);
+    gpr_free(utf8_message);
+    gpr_free(addr_str);
+    goto error;
+  }
+
+  if (listen(sock, SOMAXCONN) == SOCKET_ERROR) {
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    gpr_log(GPR_ERROR, "listen: %s", utf8_message);
+    gpr_free(utf8_message);
+    goto error;
+  }
+
+  sockname_len = sizeof(sockname_temp);
+  if (getsockname(sock, (struct sockaddr *)&sockname_temp, &sockname_len) ==
+      SOCKET_ERROR) {
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    gpr_log(GPR_ERROR, "getsockname: %s", utf8_message);
+    gpr_free(utf8_message);
+    goto error;
+  }
+
+  return grpc_sockaddr_get_port((struct sockaddr *)&sockname_temp);
+
+error:
+  if (sock != INVALID_SOCKET) closesocket(sock);
+  return -1;
+}
+
+static void decrement_active_ports_and_notify(grpc_exec_ctx *exec_ctx,
+                                              grpc_tcp_listener *sp) {
+  int notify = 0;
+  sp->shutting_down = 0;
+  gpr_mu_lock(&sp->server->mu);
+  GPR_ASSERT(sp->server->active_ports > 0);
+  if (0 == --sp->server->active_ports) {
+    notify = 1;
+  }
+  gpr_mu_unlock(&sp->server->mu);
+  if (notify) {
+    finish_shutdown(exec_ctx, sp->server);
+  }
+}
+
+/* In order to do an async accept, we need to create a socket first which
+   will be the one assigned to the new incoming connection. */
+static void start_accept(grpc_exec_ctx *exec_ctx, grpc_tcp_listener *port) {
+  SOCKET sock = INVALID_SOCKET;
+  char *message;
+  char *utf8_message;
+  BOOL success;
+  DWORD addrlen = sizeof(struct sockaddr_in6) + 16;
+  DWORD bytes_received = 0;
+
+  sock = WSASocket(AF_INET6, SOCK_STREAM, IPPROTO_TCP, NULL, 0,
+                   WSA_FLAG_OVERLAPPED);
+
+  if (sock == INVALID_SOCKET) {
+    message = "Unable to create socket: %s";
+    goto failure;
+  }
+
+  if (!grpc_tcp_prepare_socket(sock)) {
+    message = "Unable to prepare socket: %s";
+    goto failure;
+  }
+
+  /* Start the "accept" asynchronously. */
+  success = port->AcceptEx(port->socket->socket, sock, port->addresses, 0,
+                           addrlen, addrlen, &bytes_received,
+                           &port->socket->read_info.overlapped);
+
+  /* It is possible to get an accept immediately without delay. However, we
+     will still get an IOCP notification for it. So let's just ignore it. */
+  if (!success) {
+    int error = WSAGetLastError();
+    if (error != ERROR_IO_PENDING) {
+      message = "AcceptEx failed: %s";
+      goto failure;
+    }
+  }
+
+  /* We're ready to do the accept. Calling grpc_socket_notify_on_read may
+     immediately process an accept that happened in the meantime. */
+  port->new_socket = sock;
+  grpc_socket_notify_on_read(exec_ctx, port->socket, &port->on_accept);
+  return;
+
+failure:
+  if (port->shutting_down) {
+    /* We are abandoning the listener port, take that into account to prevent
+       occasional hangs on shutdown. The hang happens when sp->shutting_down
+       change is not seen by on_accept and we proceed to trying new accept,
+       but we fail there because the listening port has been closed in the
+       meantime. */
+    decrement_active_ports_and_notify(exec_ctx, port);
+    return;
+  }
+  utf8_message = gpr_format_message(WSAGetLastError());
+  gpr_log(GPR_ERROR, message, utf8_message);
+  gpr_free(utf8_message);
+  if (sock != INVALID_SOCKET) closesocket(sock);
+}
+
+/* Event manager callback when reads are ready. */
+static void on_accept(grpc_exec_ctx *exec_ctx, void *arg, bool from_iocp) {
+  grpc_tcp_listener *sp = arg;
+  grpc_tcp_server_acceptor acceptor = {sp->server, sp->port_index, 0};
+  SOCKET sock = sp->new_socket;
+  grpc_winsocket_callback_info *info = &sp->socket->read_info;
+  grpc_endpoint *ep = NULL;
+  struct sockaddr_storage peer_name;
+  char *peer_name_string;
+  char *fd_name;
+  int peer_name_len = sizeof(peer_name);
+  DWORD transfered_bytes;
+  DWORD flags;
+  BOOL wsa_success;
+  int err;
+
+  /* The general mechanism for shutting down is to queue abortion calls. While
+     this is necessary in the read/write case, it's useless for the accept
+     case. We only need to adjust the pending callback count */
+  if (!from_iocp) {
+    return;
+  }
+
+  /* The IOCP notified us of a completed operation. Let's grab the results,
+     and act accordingly. */
+  transfered_bytes = 0;
+  wsa_success = WSAGetOverlappedResult(sock, &info->overlapped,
+                                       &transfered_bytes, FALSE, &flags);
+  if (!wsa_success) {
+    if (sp->shutting_down) {
+      /* During the shutdown case, we ARE expecting an error. So that's well,
+         and we can wake up the shutdown thread. */
+      decrement_active_ports_and_notify(exec_ctx, sp);
+      return;
+    } else {
+      char *utf8_message = gpr_format_message(WSAGetLastError());
+      gpr_log(GPR_ERROR, "on_accept error: %s", utf8_message);
+      gpr_free(utf8_message);
+      closesocket(sock);
+    }
+  } else {
+    if (!sp->shutting_down) {
+      peer_name_string = NULL;
+      err = setsockopt(sock, SOL_SOCKET, SO_UPDATE_ACCEPT_CONTEXT,
+                       (char *)&sp->socket->socket, sizeof(sp->socket->socket));
+      if (err) {
+        char *utf8_message = gpr_format_message(WSAGetLastError());
+        gpr_log(GPR_ERROR, "setsockopt error: %s", utf8_message);
+        gpr_free(utf8_message);
+      }
+      err = getpeername(sock, (struct sockaddr *)&peer_name, &peer_name_len);
+      if (!err) {
+        peer_name_string = grpc_sockaddr_to_uri((struct sockaddr *)&peer_name);
+      } else {
+        char *utf8_message = gpr_format_message(WSAGetLastError());
+        gpr_log(GPR_ERROR, "getpeername error: %s", utf8_message);
+        gpr_free(utf8_message);
+      }
+      gpr_asprintf(&fd_name, "tcp_server:%s", peer_name_string);
+      ep = grpc_tcp_create(grpc_winsocket_create(sock, fd_name),
+                           peer_name_string);
+      gpr_free(fd_name);
+      gpr_free(peer_name_string);
+    } else {
+      closesocket(sock);
+    }
+  }
+
+  /* The only time we should call our callback, is where we successfully
+     managed to accept a connection, and created an endpoint. */
+  if (ep)
+    sp->server->on_accept_cb(exec_ctx, sp->server->on_accept_cb_arg, ep,
+                             &acceptor);
+  /* As we were notified from the IOCP of one and exactly one accept,
+     the former socked we created has now either been destroy or assigned
+     to the new connection. We need to create a new one for the next
+     connection. */
+  start_accept(exec_ctx, sp);
+}
+
+static grpc_tcp_listener *add_socket_to_server(grpc_tcp_server *s, SOCKET sock,
+                                               const struct sockaddr *addr,
+                                               size_t addr_len,
+                                               unsigned port_index) {
+  grpc_tcp_listener *sp = NULL;
+  int port;
+  int status;
+  GUID guid = WSAID_ACCEPTEX;
+  DWORD ioctl_num_bytes;
+  LPFN_ACCEPTEX AcceptEx;
+
+  if (sock == INVALID_SOCKET) return NULL;
+
+  /* We need to grab the AcceptEx pointer for that port, as it may be
+     interface-dependent. We'll cache it to avoid doing that again. */
+  status =
+      WSAIoctl(sock, SIO_GET_EXTENSION_FUNCTION_POINTER, &guid, sizeof(guid),
+               &AcceptEx, sizeof(AcceptEx), &ioctl_num_bytes, NULL, NULL);
+
+  if (status != 0) {
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    gpr_log(GPR_ERROR, "on_connect error: %s", utf8_message);
+    gpr_free(utf8_message);
+    closesocket(sock);
+    return NULL;
+  }
+
+  port = prepare_socket(sock, addr, addr_len);
+  if (port >= 0) {
+    gpr_mu_lock(&s->mu);
+    GPR_ASSERT(!s->on_accept_cb && "must add ports before starting server");
+    sp = gpr_malloc(sizeof(grpc_tcp_listener));
+    sp->next = NULL;
+    if (s->head == NULL) {
+      s->head = sp;
+    } else {
+      s->tail->next = sp;
+    }
+    s->tail = sp;
+    sp->server = s;
+    sp->socket = grpc_winsocket_create(sock, "listener");
+    sp->shutting_down = 0;
+    sp->AcceptEx = AcceptEx;
+    sp->new_socket = INVALID_SOCKET;
+    sp->port = port;
+    sp->port_index = port_index;
+    grpc_closure_init(&sp->on_accept, on_accept, sp);
+    GPR_ASSERT(sp->socket);
+    gpr_mu_unlock(&s->mu);
+  }
+
+  return sp;
+}
+
+int grpc_tcp_server_add_port(grpc_tcp_server *s, const void *addr,
+                             size_t addr_len) {
+  grpc_tcp_listener *sp;
+  SOCKET sock;
+  struct sockaddr_in6 addr6_v4mapped;
+  struct sockaddr_in6 wildcard;
+  struct sockaddr *allocated_addr = NULL;
+  struct sockaddr_storage sockname_temp;
+  socklen_t sockname_len;
+  int port;
+  unsigned port_index = 0;
+  if (s->tail != NULL) {
+    port_index = s->tail->port_index + 1;
+  }
+
+  /* Check if this is a wildcard port, and if so, try to keep the port the same
+     as some previously created listener. */
+  if (grpc_sockaddr_get_port(addr) == 0) {
+    for (sp = s->head; sp; sp = sp->next) {
+      sockname_len = sizeof(sockname_temp);
+      if (0 == getsockname(sp->socket->socket,
+                           (struct sockaddr *)&sockname_temp, &sockname_len)) {
+        port = grpc_sockaddr_get_port((struct sockaddr *)&sockname_temp);
+        if (port > 0) {
+          allocated_addr = malloc(addr_len);
+          memcpy(allocated_addr, addr, addr_len);
+          grpc_sockaddr_set_port(allocated_addr, port);
+          addr = allocated_addr;
+          break;
+        }
+      }
+    }
+  }
+
+  if (grpc_sockaddr_to_v4mapped(addr, &addr6_v4mapped)) {
+    addr = (const struct sockaddr *)&addr6_v4mapped;
+    addr_len = sizeof(addr6_v4mapped);
+  }
+
+  /* Treat :: or 0.0.0.0 as a family-agnostic wildcard. */
+  if (grpc_sockaddr_is_wildcard(addr, &port)) {
+    grpc_sockaddr_make_wildcard6(port, &wildcard);
+
+    addr = (struct sockaddr *)&wildcard;
+    addr_len = sizeof(wildcard);
+  }
+
+  sock = WSASocket(AF_INET6, SOCK_STREAM, IPPROTO_TCP, NULL, 0,
+                   WSA_FLAG_OVERLAPPED);
+  if (sock == INVALID_SOCKET) {
+    char *utf8_message = gpr_format_message(WSAGetLastError());
+    gpr_log(GPR_ERROR, "unable to create socket: %s", utf8_message);
+    gpr_free(utf8_message);
+  }
+
+  sp = add_socket_to_server(s, sock, addr, addr_len, port_index);
+  gpr_free(allocated_addr);
+
+  if (sp) {
+    return sp->port;
+  } else {
+    return -1;
+  }
+}
+
+unsigned grpc_tcp_server_port_fd_count(grpc_tcp_server *s,
+                                       unsigned port_index) {
+  grpc_tcp_listener *sp;
+  for (sp = s->head; sp && port_index != 0; sp = sp->next, --port_index)
+    ;
+  if (sp) {
+    return 1;
+  } else {
+    return 0;
+  }
+}
+
+int grpc_tcp_server_port_fd(grpc_tcp_server *s, unsigned port_index,
+                            unsigned fd_index) {
+  grpc_tcp_listener *sp;
+  if (fd_index != 0) {
+    /* Windows implementation has only one fd per port_index. */
+    return -1;
+  }
+  for (sp = s->head; sp && port_index != 0; sp = sp->next, --port_index)
+    ;
+  if (sp) {
+    return _open_osfhandle((intptr_t)sp->socket->socket, 0);
+  } else {
+    return -1;
+  }
+}
+
+void grpc_tcp_server_start(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s,
+                           grpc_pollset **pollset, size_t pollset_count,
+                           grpc_tcp_server_cb on_accept_cb,
+                           void *on_accept_cb_arg) {
+  grpc_tcp_listener *sp;
+  GPR_ASSERT(on_accept_cb);
+  gpr_mu_lock(&s->mu);
+  GPR_ASSERT(!s->on_accept_cb);
+  GPR_ASSERT(s->active_ports == 0);
+  s->on_accept_cb = on_accept_cb;
+  s->on_accept_cb_arg = on_accept_cb_arg;
+  for (sp = s->head; sp; sp = sp->next) {
+    start_accept(exec_ctx, sp);
+    s->active_ports++;
+  }
+  gpr_mu_unlock(&s->mu);
+}
+
+#endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/tcp_windows.c b/src/core/lib/iomgr/tcp_windows.c
new file mode 100644
index 0000000000..c1ce725f2c
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_windows.c
@@ -0,0 +1,402 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINSOCK_SOCKET
+
+#include "src/core/lib/iomgr/sockaddr_win32.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/log_win32.h>
+#include <grpc/support/slice_buffer.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/useful.h>
+
+#include "src/core/lib/iomgr/iocp_windows.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+#include "src/core/lib/iomgr/tcp_client.h"
+#include "src/core/lib/iomgr/timer.h"
+
+static int set_non_block(SOCKET sock) {
+  int status;
+  unsigned long param = 1;
+  DWORD ret;
+  status =
+      WSAIoctl(sock, FIONBIO, &param, sizeof(param), NULL, 0, &ret, NULL, NULL);
+  return status == 0;
+}
+
+static int set_dualstack(SOCKET sock) {
+  int status;
+  unsigned long param = 0;
+  status = setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (const char *)&param,
+                      sizeof(param));
+  return status == 0;
+}
+
+int grpc_tcp_prepare_socket(SOCKET sock) {
+  if (!set_non_block(sock)) return 0;
+  if (!set_dualstack(sock)) return 0;
+  return 1;
+}
+
+typedef struct grpc_tcp {
+  /* This is our C++ class derivation emulation. */
+  grpc_endpoint base;
+  /* The one socket this endpoint is using. */
+  grpc_winsocket *socket;
+  /* Refcounting how many operations are in progress. */
+  gpr_refcount refcount;
+
+  grpc_closure on_read;
+  grpc_closure on_write;
+
+  grpc_closure *read_cb;
+  grpc_closure *write_cb;
+  gpr_slice read_slice;
+  gpr_slice_buffer *write_slices;
+  gpr_slice_buffer *read_slices;
+
+  /* The IO Completion Port runs from another thread. We need some mechanism
+     to protect ourselves when requesting a shutdown. */
+  gpr_mu mu;
+  int shutting_down;
+
+  char *peer_string;
+} grpc_tcp;
+
+static void tcp_free(grpc_tcp *tcp) {
+  grpc_winsocket_destroy(tcp->socket);
+  gpr_mu_destroy(&tcp->mu);
+  gpr_free(tcp->peer_string);
+  gpr_free(tcp);
+}
+
+/*#define GRPC_TCP_REFCOUNT_DEBUG*/
+#ifdef GRPC_TCP_REFCOUNT_DEBUG
+#define TCP_UNREF(tcp, reason) tcp_unref((tcp), (reason), __FILE__, __LINE__)
+#define TCP_REF(tcp, reason) tcp_ref((tcp), (reason), __FILE__, __LINE__)
+static void tcp_unref(grpc_tcp *tcp, const char *reason, const char *file,
+                      int line) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "TCP unref %p : %s %d -> %d", tcp,
+          reason, tcp->refcount.count, tcp->refcount.count - 1);
+  if (gpr_unref(&tcp->refcount)) {
+    tcp_free(tcp);
+  }
+}
+
+static void tcp_ref(grpc_tcp *tcp, const char *reason, const char *file,
+                    int line) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "TCP   ref %p : %s %d -> %d", tcp,
+          reason, tcp->refcount.count, tcp->refcount.count + 1);
+  gpr_ref(&tcp->refcount);
+}
+#else
+#define TCP_UNREF(tcp, reason) tcp_unref((tcp))
+#define TCP_REF(tcp, reason) tcp_ref((tcp))
+static void tcp_unref(grpc_tcp *tcp) {
+  if (gpr_unref(&tcp->refcount)) {
+    tcp_free(tcp);
+  }
+}
+
+static void tcp_ref(grpc_tcp *tcp) { gpr_ref(&tcp->refcount); }
+#endif
+
+/* Asynchronous callback from the IOCP, or the background thread. */
+static void on_read(grpc_exec_ctx *exec_ctx, void *tcpp, bool success) {
+  grpc_tcp *tcp = tcpp;
+  grpc_closure *cb = tcp->read_cb;
+  grpc_winsocket *socket = tcp->socket;
+  gpr_slice sub;
+  grpc_winsocket_callback_info *info = &socket->read_info;
+
+  if (success) {
+    if (info->wsa_error != 0 && !tcp->shutting_down) {
+      if (info->wsa_error != WSAECONNRESET) {
+        char *utf8_message = gpr_format_message(info->wsa_error);
+        gpr_log(GPR_ERROR, "ReadFile overlapped error: %s", utf8_message);
+        gpr_free(utf8_message);
+      }
+      success = 0;
+      gpr_slice_unref(tcp->read_slice);
+    } else {
+      if (info->bytes_transfered != 0 && !tcp->shutting_down) {
+        sub = gpr_slice_sub_no_ref(tcp->read_slice, 0, info->bytes_transfered);
+        gpr_slice_buffer_add(tcp->read_slices, sub);
+        success = 1;
+      } else {
+        gpr_slice_unref(tcp->read_slice);
+        success = 0;
+      }
+    }
+  }
+
+  tcp->read_cb = NULL;
+  TCP_UNREF(tcp, "read");
+  if (cb) {
+    cb->cb(exec_ctx, cb->cb_arg, success);
+  }
+}
+
+static void win_read(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                     gpr_slice_buffer *read_slices, grpc_closure *cb) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  grpc_winsocket *handle = tcp->socket;
+  grpc_winsocket_callback_info *info = &handle->read_info;
+  int status;
+  DWORD bytes_read = 0;
+  DWORD flags = 0;
+  WSABUF buffer;
+
+  if (tcp->shutting_down) {
+    grpc_exec_ctx_enqueue(exec_ctx, cb, false, NULL);
+    return;
+  }
+
+  tcp->read_cb = cb;
+  tcp->read_slices = read_slices;
+  gpr_slice_buffer_reset_and_unref(read_slices);
+
+  tcp->read_slice = gpr_slice_malloc(8192);
+
+  buffer.len = (ULONG)GPR_SLICE_LENGTH(
+      tcp->read_slice);  // we know slice size fits in 32bit.
+  buffer.buf = (char *)GPR_SLICE_START_PTR(tcp->read_slice);
+
+  TCP_REF(tcp, "read");
+
+  /* First let's try a synchronous, non-blocking read. */
+  status =
+      WSARecv(tcp->socket->socket, &buffer, 1, &bytes_read, &flags, NULL, NULL);
+  info->wsa_error = status == 0 ? 0 : WSAGetLastError();
+
+  /* Did we get data immediately ? Yay. */
+  if (info->wsa_error != WSAEWOULDBLOCK) {
+    info->bytes_transfered = bytes_read;
+    grpc_exec_ctx_enqueue(exec_ctx, &tcp->on_read, true, NULL);
+    return;
+  }
+
+  /* Otherwise, let's retry, by queuing a read. */
+  memset(&tcp->socket->read_info.overlapped, 0, sizeof(OVERLAPPED));
+  status = WSARecv(tcp->socket->socket, &buffer, 1, &bytes_read, &flags,
+                   &info->overlapped, NULL);
+
+  if (status != 0) {
+    int wsa_error = WSAGetLastError();
+    if (wsa_error != WSA_IO_PENDING) {
+      info->wsa_error = wsa_error;
+      grpc_exec_ctx_enqueue(exec_ctx, &tcp->on_read, false, NULL);
+      return;
+    }
+  }
+
+  grpc_socket_notify_on_read(exec_ctx, tcp->socket, &tcp->on_read);
+}
+
+/* Asynchronous callback from the IOCP, or the background thread. */
+static void on_write(grpc_exec_ctx *exec_ctx, void *tcpp, bool success) {
+  grpc_tcp *tcp = (grpc_tcp *)tcpp;
+  grpc_winsocket *handle = tcp->socket;
+  grpc_winsocket_callback_info *info = &handle->write_info;
+  grpc_closure *cb;
+
+  gpr_mu_lock(&tcp->mu);
+  cb = tcp->write_cb;
+  tcp->write_cb = NULL;
+  gpr_mu_unlock(&tcp->mu);
+
+  if (success) {
+    if (info->wsa_error != 0) {
+      if (info->wsa_error != WSAECONNRESET) {
+        char *utf8_message = gpr_format_message(info->wsa_error);
+        gpr_log(GPR_ERROR, "WSASend overlapped error: %s", utf8_message);
+        gpr_free(utf8_message);
+      }
+      success = 0;
+    } else {
+      GPR_ASSERT(info->bytes_transfered == tcp->write_slices->length);
+    }
+  }
+
+  TCP_UNREF(tcp, "write");
+  cb->cb(exec_ctx, cb->cb_arg, success);
+}
+
+/* Initiates a write. */
+static void win_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                      gpr_slice_buffer *slices, grpc_closure *cb) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  grpc_winsocket *socket = tcp->socket;
+  grpc_winsocket_callback_info *info = &socket->write_info;
+  unsigned i;
+  DWORD bytes_sent;
+  int status;
+  WSABUF local_buffers[16];
+  WSABUF *allocated = NULL;
+  WSABUF *buffers = local_buffers;
+  size_t len;
+
+  if (tcp->shutting_down) {
+    grpc_exec_ctx_enqueue(exec_ctx, cb, false, NULL);
+    return;
+  }
+
+  tcp->write_cb = cb;
+  tcp->write_slices = slices;
+  GPR_ASSERT(tcp->write_slices->count <= UINT_MAX);
+  if (tcp->write_slices->count > GPR_ARRAY_SIZE(local_buffers)) {
+    buffers = (WSABUF *)gpr_malloc(sizeof(WSABUF) * tcp->write_slices->count);
+    allocated = buffers;
+  }
+
+  for (i = 0; i < tcp->write_slices->count; i++) {
+    len = GPR_SLICE_LENGTH(tcp->write_slices->slices[i]);
+    GPR_ASSERT(len <= ULONG_MAX);
+    buffers[i].len = (ULONG)len;
+    buffers[i].buf = (char *)GPR_SLICE_START_PTR(tcp->write_slices->slices[i]);
+  }
+
+  /* First, let's try a synchronous, non-blocking write. */
+  status = WSASend(socket->socket, buffers, (DWORD)tcp->write_slices->count,
+                   &bytes_sent, 0, NULL, NULL);
+  info->wsa_error = status == 0 ? 0 : WSAGetLastError();
+
+  /* We would kind of expect to get a WSAEWOULDBLOCK here, especially on a busy
+     connection that has its send queue filled up. But if we don't, then we can
+     avoid doing an async write operation at all. */
+  if (info->wsa_error != WSAEWOULDBLOCK) {
+    bool ok = false;
+    if (status == 0) {
+      ok = true;
+      GPR_ASSERT(bytes_sent == tcp->write_slices->length);
+    } else {
+      if (info->wsa_error != WSAECONNRESET) {
+        char *utf8_message = gpr_format_message(info->wsa_error);
+        gpr_log(GPR_ERROR, "WSASend error: %s", utf8_message);
+        gpr_free(utf8_message);
+      }
+    }
+    if (allocated) gpr_free(allocated);
+    grpc_exec_ctx_enqueue(exec_ctx, cb, ok, NULL);
+    return;
+  }
+
+  TCP_REF(tcp, "write");
+
+  /* If we got a WSAEWOULDBLOCK earlier, then we need to re-do the same
+     operation, this time asynchronously. */
+  memset(&socket->write_info.overlapped, 0, sizeof(OVERLAPPED));
+  status = WSASend(socket->socket, buffers, (DWORD)tcp->write_slices->count,
+                   &bytes_sent, 0, &socket->write_info.overlapped, NULL);
+  if (allocated) gpr_free(allocated);
+
+  if (status != 0) {
+    int wsa_error = WSAGetLastError();
+    if (wsa_error != WSA_IO_PENDING) {
+      TCP_UNREF(tcp, "write");
+      grpc_exec_ctx_enqueue(exec_ctx, cb, false, NULL);
+      return;
+    }
+  }
+
+  /* As all is now setup, we can now ask for the IOCP notification. It may
+     trigger the callback immediately however, but no matter. */
+  grpc_socket_notify_on_write(exec_ctx, socket, &tcp->on_write);
+}
+
+static void win_add_to_pollset(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                               grpc_pollset *ps) {
+  grpc_tcp *tcp;
+  (void)ps;
+  tcp = (grpc_tcp *)ep;
+  grpc_iocp_add_socket(tcp->socket);
+}
+
+static void win_add_to_pollset_set(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
+                                   grpc_pollset_set *pss) {
+  grpc_tcp *tcp;
+  (void)pss;
+  tcp = (grpc_tcp *)ep;
+  grpc_iocp_add_socket(tcp->socket);
+}
+
+/* Initiates a shutdown of the TCP endpoint. This will queue abort callbacks
+   for the potential read and write operations. It is up to the caller to
+   guarantee this isn't called in parallel to a read or write request, so
+   we're not going to protect against these. However the IO Completion Port
+   callback will happen from another thread, so we need to protect against
+   concurrent access of the data structure in that regard. */
+static void win_shutdown(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  gpr_mu_lock(&tcp->mu);
+  /* At that point, what may happen is that we're already inside the IOCP
+     callback. See the comments in on_read and on_write. */
+  tcp->shutting_down = 1;
+  grpc_winsocket_shutdown(tcp->socket);
+  gpr_mu_unlock(&tcp->mu);
+}
+
+static void win_destroy(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  TCP_UNREF(tcp, "destroy");
+}
+
+static char *win_get_peer(grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  return gpr_strdup(tcp->peer_string);
+}
+
+static grpc_endpoint_vtable vtable = {
+    win_read,     win_write,   win_add_to_pollset, win_add_to_pollset_set,
+    win_shutdown, win_destroy, win_get_peer};
+
+grpc_endpoint *grpc_tcp_create(grpc_winsocket *socket, char *peer_string) {
+  grpc_tcp *tcp = (grpc_tcp *)gpr_malloc(sizeof(grpc_tcp));
+  memset(tcp, 0, sizeof(grpc_tcp));
+  tcp->base.vtable = &vtable;
+  tcp->socket = socket;
+  gpr_mu_init(&tcp->mu);
+  gpr_ref_init(&tcp->refcount, 1);
+  grpc_closure_init(&tcp->on_read, on_read, tcp);
+  grpc_closure_init(&tcp->on_write, on_write, tcp);
+  tcp->peer_string = gpr_strdup(peer_string);
+  return &tcp->base;
+}
+
+#endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/lib/iomgr/tcp_windows.h b/src/core/lib/iomgr/tcp_windows.h
new file mode 100644
index 0000000000..7a9ebd85eb
--- /dev/null
+++ b/src/core/lib/iomgr/tcp_windows.h
@@ -0,0 +1,57 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_TCP_WINDOWS_H
+#define GRPC_CORE_LIB_IOMGR_TCP_WINDOWS_H
+/*
+   Low level TCP "bottom half" implementation, for use by transports built on
+   top of a TCP connection.
+
+   Note that this file does not (yet) include APIs for creating the socket in
+   the first place.
+
+   All calls passing slice transfer ownership of a slice refcount unless
+   otherwise specified.
+*/
+
+#include "src/core/lib/iomgr/endpoint.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+
+/* Create a tcp endpoint given a winsock handle.
+ * Takes ownership of the handle.
+ */
+grpc_endpoint *grpc_tcp_create(grpc_winsocket *socket, char *peer_string);
+
+int grpc_tcp_prepare_socket(SOCKET sock);
+
+#endif /* GRPC_CORE_LIB_IOMGR_TCP_WINDOWS_H */
diff --git a/src/core/lib/iomgr/time_averaged_stats.c b/src/core/lib/iomgr/time_averaged_stats.c
new file mode 100644
index 0000000000..f24d68087e
--- /dev/null
+++ b/src/core/lib/iomgr/time_averaged_stats.c
@@ -0,0 +1,77 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/time_averaged_stats.h"
+
+void grpc_time_averaged_stats_init(grpc_time_averaged_stats* stats,
+                                   double init_avg, double regress_weight,
+                                   double persistence_factor) {
+  stats->init_avg = init_avg;
+  stats->regress_weight = regress_weight;
+  stats->persistence_factor = persistence_factor;
+  stats->batch_total_value = 0;
+  stats->batch_num_samples = 0;
+  stats->aggregate_total_weight = 0;
+  stats->aggregate_weighted_avg = init_avg;
+}
+
+void grpc_time_averaged_stats_add_sample(grpc_time_averaged_stats* stats,
+                                         double value) {
+  stats->batch_total_value += value;
+  ++stats->batch_num_samples;
+}
+
+double grpc_time_averaged_stats_update_average(
+    grpc_time_averaged_stats* stats) {
+  /* Start with the current batch: */
+  double weighted_sum = stats->batch_total_value;
+  double total_weight = stats->batch_num_samples;
+  if (stats->regress_weight > 0) {
+    /* Add in the regression towards init_avg_: */
+    weighted_sum += stats->regress_weight * stats->init_avg;
+    total_weight += stats->regress_weight;
+  }
+  if (stats->persistence_factor > 0) {
+    /* Add in the persistence: */
+    const double prev_sample_weight =
+        stats->persistence_factor * stats->aggregate_total_weight;
+    weighted_sum += prev_sample_weight * stats->aggregate_weighted_avg;
+    total_weight += prev_sample_weight;
+  }
+  stats->aggregate_weighted_avg =
+      (total_weight > 0) ? (weighted_sum / total_weight) : stats->init_avg;
+  stats->aggregate_total_weight = total_weight;
+  stats->batch_num_samples = 0;
+  stats->batch_total_value = 0;
+  return stats->aggregate_weighted_avg;
+}
diff --git a/src/core/lib/iomgr/time_averaged_stats.h b/src/core/lib/iomgr/time_averaged_stats.h
new file mode 100644
index 0000000000..4a662e17ec
--- /dev/null
+++ b/src/core/lib/iomgr/time_averaged_stats.h
@@ -0,0 +1,88 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_TIME_AVERAGED_STATS_H
+#define GRPC_CORE_LIB_IOMGR_TIME_AVERAGED_STATS_H
+
+/* This tracks a time-decaying weighted average.  It works by collecting
+   batches of samples and then mixing their average into a time-decaying
+   weighted mean.  It is designed for batch operations where we do many adds
+   before updating the average. */
+
+typedef struct {
+  /* The initial average value.  This is the reported average until the first
+     grpc_time_averaged_stats_update_average call.  If a positive regress_weight
+     is used, we also regress towards this value on each update. */
+  double init_avg;
+  /* The sample weight of "init_avg" that is mixed in with each call to
+     grpc_time_averaged_stats_update_average.  If the calls to
+     grpc_time_averaged_stats_add_sample stop, this will cause the average to
+     regress back to the mean.  This should be non-negative.  Set it to 0 to
+     disable the bias.  A value of 1 has the effect of adding in 1 bonus sample
+     with value init_avg to each sample period. */
+  double regress_weight;
+  /* This determines the rate of decay of the time-averaging from one period
+     to the next by scaling the aggregate_total_weight of samples from prior
+     periods when combining with the latest period.  It should be in the range
+     [0,1].  A higher value adapts more slowly.  With a value of 0.5, if the
+     batches each have k samples, the samples_in_avg_ will grow to 2 k, so the
+     weighting of the time average will eventually be 1/3 new batch and 2/3
+     old average. */
+  double persistence_factor;
+
+  /* The total value of samples since the last UpdateAverage(). */
+  double batch_total_value;
+  /* The number of samples since the last UpdateAverage(). */
+  double batch_num_samples;
+  /* The time-decayed sum of batch_num_samples_ over previous batches.  This is
+     the "weight" of the old aggregate_weighted_avg_ when updating the
+     average. */
+  double aggregate_total_weight;
+  /* A time-decayed average of the (batch_total_value_ / batch_num_samples_),
+     computed by decaying the samples_in_avg_ weight in the weighted average. */
+  double aggregate_weighted_avg;
+} grpc_time_averaged_stats;
+
+/* See the comments on the members above for an explanation of init_avg,
+   regress_weight, and persistence_factor. */
+void grpc_time_averaged_stats_init(grpc_time_averaged_stats* stats,
+                                   double init_avg, double regress_weight,
+                                   double persistence_factor);
+/* Add a sample to the current batch. */
+void grpc_time_averaged_stats_add_sample(grpc_time_averaged_stats* stats,
+                                         double value);
+/* Complete a batch and compute the new estimate of the average sample
+   value. */
+double grpc_time_averaged_stats_update_average(grpc_time_averaged_stats* stats);
+
+#endif /* GRPC_CORE_LIB_IOMGR_TIME_AVERAGED_STATS_H */
diff --git a/src/core/lib/iomgr/timer.c b/src/core/lib/iomgr/timer.c
new file mode 100644
index 0000000000..4748f9b270
--- /dev/null
+++ b/src/core/lib/iomgr/timer.c
@@ -0,0 +1,356 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/timer.h"
+
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/useful.h>
+#include "src/core/lib/iomgr/time_averaged_stats.h"
+#include "src/core/lib/iomgr/timer_heap.h"
+
+#define INVALID_HEAP_INDEX 0xffffffffu
+
+#define LOG2_NUM_SHARDS 5
+#define NUM_SHARDS (1 << LOG2_NUM_SHARDS)
+#define ADD_DEADLINE_SCALE 0.33
+#define MIN_QUEUE_WINDOW_DURATION 0.01
+#define MAX_QUEUE_WINDOW_DURATION 1
+
+typedef struct {
+  gpr_mu mu;
+  grpc_time_averaged_stats stats;
+  /* All and only timers with deadlines <= this will be in the heap. */
+  gpr_timespec queue_deadline_cap;
+  gpr_timespec min_deadline;
+  /* Index in the g_shard_queue */
+  uint32_t shard_queue_index;
+  /* This holds all timers with deadlines < queue_deadline_cap. Timers in this
+     list have the top bit of their deadline set to 0. */
+  grpc_timer_heap heap;
+  /* This holds timers whose deadline is >= queue_deadline_cap. */
+  grpc_timer list;
+} shard_type;
+
+/* Protects g_shard_queue */
+static gpr_mu g_mu;
+/* Allow only one run_some_expired_timers at once */
+static gpr_mu g_checker_mu;
+static gpr_clock_type g_clock_type;
+static shard_type g_shards[NUM_SHARDS];
+/* Protected by g_mu */
+static shard_type *g_shard_queue[NUM_SHARDS];
+
+static int run_some_expired_timers(grpc_exec_ctx *exec_ctx, gpr_timespec now,
+                                   gpr_timespec *next, int success);
+
+static gpr_timespec compute_min_deadline(shard_type *shard) {
+  return grpc_timer_heap_is_empty(&shard->heap)
+             ? shard->queue_deadline_cap
+             : grpc_timer_heap_top(&shard->heap)->deadline;
+}
+
+void grpc_timer_list_init(gpr_timespec now) {
+  uint32_t i;
+
+  gpr_mu_init(&g_mu);
+  gpr_mu_init(&g_checker_mu);
+  g_clock_type = now.clock_type;
+
+  for (i = 0; i < NUM_SHARDS; i++) {
+    shard_type *shard = &g_shards[i];
+    gpr_mu_init(&shard->mu);
+    grpc_time_averaged_stats_init(&shard->stats, 1.0 / ADD_DEADLINE_SCALE, 0.1,
+                                  0.5);
+    shard->queue_deadline_cap = now;
+    shard->shard_queue_index = i;
+    grpc_timer_heap_init(&shard->heap);
+    shard->list.next = shard->list.prev = &shard->list;
+    shard->min_deadline = compute_min_deadline(shard);
+    g_shard_queue[i] = shard;
+  }
+}
+
+void grpc_timer_list_shutdown(grpc_exec_ctx *exec_ctx) {
+  int i;
+  run_some_expired_timers(exec_ctx, gpr_inf_future(g_clock_type), NULL, 0);
+  for (i = 0; i < NUM_SHARDS; i++) {
+    shard_type *shard = &g_shards[i];
+    gpr_mu_destroy(&shard->mu);
+    grpc_timer_heap_destroy(&shard->heap);
+  }
+  gpr_mu_destroy(&g_mu);
+  gpr_mu_destroy(&g_checker_mu);
+}
+
+/* This is a cheap, but good enough, pointer hash for sharding the tasks: */
+static size_t shard_idx(const grpc_timer *info) {
+  size_t x = (size_t)info;
+  return ((x >> 4) ^ (x >> 9) ^ (x >> 14)) & (NUM_SHARDS - 1);
+}
+
+static double ts_to_dbl(gpr_timespec ts) {
+  return (double)ts.tv_sec + 1e-9 * ts.tv_nsec;
+}
+
+static gpr_timespec dbl_to_ts(double d) {
+  gpr_timespec ts;
+  ts.tv_sec = (int64_t)d;
+  ts.tv_nsec = (int32_t)(1e9 * (d - (double)ts.tv_sec));
+  ts.clock_type = GPR_TIMESPAN;
+  return ts;
+}
+
+static void list_join(grpc_timer *head, grpc_timer *timer) {
+  timer->next = head;
+  timer->prev = head->prev;
+  timer->next->prev = timer->prev->next = timer;
+}
+
+static void list_remove(grpc_timer *timer) {
+  timer->next->prev = timer->prev;
+  timer->prev->next = timer->next;
+}
+
+static void swap_adjacent_shards_in_queue(uint32_t first_shard_queue_index) {
+  shard_type *temp;
+  temp = g_shard_queue[first_shard_queue_index];
+  g_shard_queue[first_shard_queue_index] =
+      g_shard_queue[first_shard_queue_index + 1];
+  g_shard_queue[first_shard_queue_index + 1] = temp;
+  g_shard_queue[first_shard_queue_index]->shard_queue_index =
+      first_shard_queue_index;
+  g_shard_queue[first_shard_queue_index + 1]->shard_queue_index =
+      first_shard_queue_index + 1;
+}
+
+static void note_deadline_change(shard_type *shard) {
+  while (shard->shard_queue_index > 0 &&
+         gpr_time_cmp(
+             shard->min_deadline,
+             g_shard_queue[shard->shard_queue_index - 1]->min_deadline) < 0) {
+    swap_adjacent_shards_in_queue(shard->shard_queue_index - 1);
+  }
+  while (shard->shard_queue_index < NUM_SHARDS - 1 &&
+         gpr_time_cmp(
+             shard->min_deadline,
+             g_shard_queue[shard->shard_queue_index + 1]->min_deadline) > 0) {
+    swap_adjacent_shards_in_queue(shard->shard_queue_index);
+  }
+}
+
+void grpc_timer_init(grpc_exec_ctx *exec_ctx, grpc_timer *timer,
+                     gpr_timespec deadline, grpc_iomgr_cb_func timer_cb,
+                     void *timer_cb_arg, gpr_timespec now) {
+  int is_first_timer = 0;
+  shard_type *shard = &g_shards[shard_idx(timer)];
+  GPR_ASSERT(deadline.clock_type == g_clock_type);
+  GPR_ASSERT(now.clock_type == g_clock_type);
+  grpc_closure_init(&timer->closure, timer_cb, timer_cb_arg);
+  timer->deadline = deadline;
+  timer->triggered = 0;
+
+  /* TODO(ctiller): check deadline expired */
+
+  gpr_mu_lock(&shard->mu);
+  grpc_time_averaged_stats_add_sample(&shard->stats,
+                                      ts_to_dbl(gpr_time_sub(deadline, now)));
+  if (gpr_time_cmp(deadline, shard->queue_deadline_cap) < 0) {
+    is_first_timer = grpc_timer_heap_add(&shard->heap, timer);
+  } else {
+    timer->heap_index = INVALID_HEAP_INDEX;
+    list_join(&shard->list, timer);
+  }
+  gpr_mu_unlock(&shard->mu);
+
+  /* Deadline may have decreased, we need to adjust the master queue.  Note
+     that there is a potential racy unlocked region here.  There could be a
+     reordering of multiple grpc_timer_init calls, at this point, but the < test
+     below should ensure that we err on the side of caution.  There could
+     also be a race with grpc_timer_check, which might beat us to the lock.  In
+     that case, it is possible that the timer that we added will have already
+     run by the time we hold the lock, but that too is a safe error.
+     Finally, it's possible that the grpc_timer_check that intervened failed to
+     trigger the new timer because the min_deadline hadn't yet been reduced.
+     In that case, the timer will simply have to wait for the next
+     grpc_timer_check. */
+  if (is_first_timer) {
+    gpr_mu_lock(&g_mu);
+    if (gpr_time_cmp(deadline, shard->min_deadline) < 0) {
+      gpr_timespec old_min_deadline = g_shard_queue[0]->min_deadline;
+      shard->min_deadline = deadline;
+      note_deadline_change(shard);
+      if (shard->shard_queue_index == 0 &&
+          gpr_time_cmp(deadline, old_min_deadline) < 0) {
+        grpc_kick_poller();
+      }
+    }
+    gpr_mu_unlock(&g_mu);
+  }
+}
+
+void grpc_timer_cancel(grpc_exec_ctx *exec_ctx, grpc_timer *timer) {
+  shard_type *shard = &g_shards[shard_idx(timer)];
+  gpr_mu_lock(&shard->mu);
+  if (!timer->triggered) {
+    grpc_exec_ctx_enqueue(exec_ctx, &timer->closure, false, NULL);
+    timer->triggered = 1;
+    if (timer->heap_index == INVALID_HEAP_INDEX) {
+      list_remove(timer);
+    } else {
+      grpc_timer_heap_remove(&shard->heap, timer);
+    }
+  }
+  gpr_mu_unlock(&shard->mu);
+}
+
+/* This is called when the queue is empty and "now" has reached the
+   queue_deadline_cap.  We compute a new queue deadline and then scan the map
+   for timers that fall at or under it.  Returns true if the queue is no
+   longer empty.
+   REQUIRES: shard->mu locked */
+static int refill_queue(shard_type *shard, gpr_timespec now) {
+  /* Compute the new queue window width and bound by the limits: */
+  double computed_deadline_delta =
+      grpc_time_averaged_stats_update_average(&shard->stats) *
+      ADD_DEADLINE_SCALE;
+  double deadline_delta =
+      GPR_CLAMP(computed_deadline_delta, MIN_QUEUE_WINDOW_DURATION,
+                MAX_QUEUE_WINDOW_DURATION);
+  grpc_timer *timer, *next;
+
+  /* Compute the new cap and put all timers under it into the queue: */
+  shard->queue_deadline_cap = gpr_time_add(
+      gpr_time_max(now, shard->queue_deadline_cap), dbl_to_ts(deadline_delta));
+  for (timer = shard->list.next; timer != &shard->list; timer = next) {
+    next = timer->next;
+
+    if (gpr_time_cmp(timer->deadline, shard->queue_deadline_cap) < 0) {
+      list_remove(timer);
+      grpc_timer_heap_add(&shard->heap, timer);
+    }
+  }
+  return !grpc_timer_heap_is_empty(&shard->heap);
+}
+
+/* This pops the next non-cancelled timer with deadline <= now from the queue,
+   or returns NULL if there isn't one.
+   REQUIRES: shard->mu locked */
+static grpc_timer *pop_one(shard_type *shard, gpr_timespec now) {
+  grpc_timer *timer;
+  for (;;) {
+    if (grpc_timer_heap_is_empty(&shard->heap)) {
+      if (gpr_time_cmp(now, shard->queue_deadline_cap) < 0) return NULL;
+      if (!refill_queue(shard, now)) return NULL;
+    }
+    timer = grpc_timer_heap_top(&shard->heap);
+    if (gpr_time_cmp(timer->deadline, now) > 0) return NULL;
+    timer->triggered = 1;
+    grpc_timer_heap_pop(&shard->heap);
+    return timer;
+  }
+}
+
+/* REQUIRES: shard->mu unlocked */
+static size_t pop_timers(grpc_exec_ctx *exec_ctx, shard_type *shard,
+                         gpr_timespec now, gpr_timespec *new_min_deadline,
+                         int success) {
+  size_t n = 0;
+  grpc_timer *timer;
+  gpr_mu_lock(&shard->mu);
+  while ((timer = pop_one(shard, now))) {
+    grpc_exec_ctx_enqueue(exec_ctx, &timer->closure, success, NULL);
+    n++;
+  }
+  *new_min_deadline = compute_min_deadline(shard);
+  gpr_mu_unlock(&shard->mu);
+  return n;
+}
+
+static int run_some_expired_timers(grpc_exec_ctx *exec_ctx, gpr_timespec now,
+                                   gpr_timespec *next, int success) {
+  size_t n = 0;
+
+  /* TODO(ctiller): verify that there are any timers (atomically) here */
+
+  if (gpr_mu_trylock(&g_checker_mu)) {
+    gpr_mu_lock(&g_mu);
+
+    while (gpr_time_cmp(g_shard_queue[0]->min_deadline, now) < 0) {
+      gpr_timespec new_min_deadline;
+
+      /* For efficiency, we pop as many available timers as we can from the
+         shard.  This may violate perfect timer deadline ordering, but that
+         shouldn't be a big deal because we don't make ordering guarantees. */
+      n += pop_timers(exec_ctx, g_shard_queue[0], now, &new_min_deadline,
+                      success);
+
+      /* An grpc_timer_init() on the shard could intervene here, adding a new
+         timer that is earlier than new_min_deadline.  However,
+         grpc_timer_init() will block on the master_lock before it can call
+         set_min_deadline, so this one will complete first and then the Addtimer
+         will reduce the min_deadline (perhaps unnecessarily). */
+      g_shard_queue[0]->min_deadline = new_min_deadline;
+      note_deadline_change(g_shard_queue[0]);
+    }
+
+    if (next) {
+      *next = gpr_time_min(*next, g_shard_queue[0]->min_deadline);
+    }
+
+    gpr_mu_unlock(&g_mu);
+    gpr_mu_unlock(&g_checker_mu);
+  } else if (next != NULL) {
+    /* TODO(ctiller): this forces calling code to do an short poll, and
+       then retry the timer check (because this time through the timer list was
+       contended).
+
+       We could reduce the cost here dramatically by keeping a count of how many
+       currently active pollers got through the uncontended case above
+       successfully, and waking up other pollers IFF that count drops to zero.
+
+       Once that count is in place, this entire else branch could disappear. */
+    *next = gpr_time_min(
+        *next, gpr_time_add(now, gpr_time_from_millis(1, GPR_TIMESPAN)));
+  }
+
+  return (int)n;
+}
+
+bool grpc_timer_check(grpc_exec_ctx *exec_ctx, gpr_timespec now,
+                      gpr_timespec *next) {
+  GPR_ASSERT(now.clock_type == g_clock_type);
+  return run_some_expired_timers(
+      exec_ctx, now, next,
+      gpr_time_cmp(now, gpr_inf_future(now.clock_type)) != 0);
+}
diff --git a/src/core/lib/iomgr/timer.h b/src/core/lib/iomgr/timer.h
new file mode 100644
index 0000000000..54f301c5ed
--- /dev/null
+++ b/src/core/lib/iomgr/timer.h
@@ -0,0 +1,108 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_TIMER_H
+#define GRPC_CORE_LIB_IOMGR_TIMER_H
+
+#include <grpc/support/port_platform.h>
+#include <grpc/support/time.h>
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/iomgr.h"
+
+typedef struct grpc_timer {
+  gpr_timespec deadline;
+  uint32_t heap_index; /* INVALID_HEAP_INDEX if not in heap */
+  int triggered;
+  struct grpc_timer *next;
+  struct grpc_timer *prev;
+  grpc_closure closure;
+} grpc_timer;
+
+/* Initialize *timer. When expired or canceled, timer_cb will be called with
+   *timer_cb_arg and status to indicate if it expired (SUCCESS) or was
+   canceled (CANCELLED). timer_cb is guaranteed to be called exactly once,
+   and application code should check the status to determine how it was
+   invoked. The application callback is also responsible for maintaining
+   information about when to free up any user-level state. */
+void grpc_timer_init(grpc_exec_ctx *exec_ctx, grpc_timer *timer,
+                     gpr_timespec deadline, grpc_iomgr_cb_func timer_cb,
+                     void *timer_cb_arg, gpr_timespec now);
+
+/* Note that there is no timer destroy function. This is because the
+   timer is a one-time occurrence with a guarantee that the callback will
+   be called exactly once, either at expiration or cancellation. Thus, all
+   the internal timer event management state is destroyed just before
+   that callback is invoked. If the user has additional state associated with
+   the timer, the user is responsible for determining when it is safe to
+   destroy that state. */
+
+/* Cancel an *timer.
+   There are three cases:
+   1. We normally cancel the timer
+   2. The timer has already run
+   3. We can't cancel the timer because it is "in flight".
+
+   In all of these cases, the cancellation is still considered successful.
+   They are essentially distinguished in that the timer_cb will be run
+   exactly once from either the cancellation (with status CANCELLED)
+   or from the activation (with status SUCCESS)
+
+   Note carefully that the callback function MAY occur in the same callstack
+   as grpc_timer_cancel. It's expected that most timers will be cancelled (their
+   primary use is to implement deadlines), and so this code is optimized such
+   that cancellation costs as little as possible. Making callbacks run inline
+   matches this aim.
+
+   Requires:  cancel() must happen after add() on a given timer */
+void grpc_timer_cancel(grpc_exec_ctx *exec_ctx, grpc_timer *timer);
+
+/* iomgr internal api for dealing with timers */
+
+/* Check for timers to be run, and run them.
+   Return true if timer callbacks were executed.
+   Drops drop_mu if it is non-null before executing callbacks.
+   If next is non-null, TRY to update *next with the next running timer
+   IF that timer occurs before *next current value.
+   *next is never guaranteed to be updated on any given execution; however,
+   with high probability at least one thread in the system will see an update
+   at any time slice. */
+bool grpc_timer_check(grpc_exec_ctx *exec_ctx, gpr_timespec now,
+                      gpr_timespec *next);
+void grpc_timer_list_init(gpr_timespec now);
+void grpc_timer_list_shutdown(grpc_exec_ctx *exec_ctx);
+
+/* the following must be implemented by each iomgr implementation */
+
+void grpc_kick_poller(void);
+
+#endif /* GRPC_CORE_LIB_IOMGR_TIMER_H */
diff --git a/src/core/lib/iomgr/timer_heap.c b/src/core/lib/iomgr/timer_heap.c
new file mode 100644
index 0000000000..d43b6ccf75
--- /dev/null
+++ b/src/core/lib/iomgr/timer_heap.c
@@ -0,0 +1,146 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/timer_heap.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/useful.h>
+
+/* Adjusts a heap so as to move a hole at position i closer to the root,
+   until a suitable position is found for element t. Then, copies t into that
+   position. This functor is called each time immediately after modifying a
+   value in the underlying container, with the offset of the modified element as
+   its argument. */
+static void adjust_upwards(grpc_timer **first, uint32_t i, grpc_timer *t) {
+  while (i > 0) {
+    uint32_t parent = (uint32_t)(((int)i - 1) / 2);
+    if (gpr_time_cmp(first[parent]->deadline, t->deadline) <= 0) break;
+    first[i] = first[parent];
+    first[i]->heap_index = i;
+    i = parent;
+  }
+  first[i] = t;
+  t->heap_index = i;
+}
+
+/* Adjusts a heap so as to move a hole at position i farther away from the root,
+   until a suitable position is found for element t.  Then, copies t into that
+   position. */
+static void adjust_downwards(grpc_timer **first, uint32_t i, uint32_t length,
+                             grpc_timer *t) {
+  for (;;) {
+    uint32_t left_child = 1u + 2u * i;
+    if (left_child >= length) break;
+    uint32_t right_child = left_child + 1;
+    uint32_t next_i = right_child < length &&
+                              gpr_time_cmp(first[left_child]->deadline,
+                                           first[right_child]->deadline) > 0
+                          ? right_child
+                          : left_child;
+    if (gpr_time_cmp(t->deadline, first[next_i]->deadline) <= 0) break;
+    first[i] = first[next_i];
+    first[i]->heap_index = i;
+    i = next_i;
+  }
+  first[i] = t;
+  t->heap_index = i;
+}
+
+#define SHRINK_MIN_ELEMS 8
+#define SHRINK_FULLNESS_FACTOR 2
+
+static void maybe_shrink(grpc_timer_heap *heap) {
+  if (heap->timer_count >= 8 &&
+      heap->timer_count <= heap->timer_capacity / SHRINK_FULLNESS_FACTOR / 2) {
+    heap->timer_capacity = heap->timer_count * SHRINK_FULLNESS_FACTOR;
+    heap->timers =
+        gpr_realloc(heap->timers, heap->timer_capacity * sizeof(grpc_timer *));
+  }
+}
+
+static void note_changed_priority(grpc_timer_heap *heap, grpc_timer *timer) {
+  uint32_t i = timer->heap_index;
+  uint32_t parent = (uint32_t)(((int)i - 1) / 2);
+  if (gpr_time_cmp(heap->timers[parent]->deadline, timer->deadline) > 0) {
+    adjust_upwards(heap->timers, i, timer);
+  } else {
+    adjust_downwards(heap->timers, i, heap->timer_count, timer);
+  }
+}
+
+void grpc_timer_heap_init(grpc_timer_heap *heap) {
+  memset(heap, 0, sizeof(*heap));
+}
+
+void grpc_timer_heap_destroy(grpc_timer_heap *heap) { gpr_free(heap->timers); }
+
+int grpc_timer_heap_add(grpc_timer_heap *heap, grpc_timer *timer) {
+  if (heap->timer_count == heap->timer_capacity) {
+    heap->timer_capacity =
+        GPR_MAX(heap->timer_capacity + 1, heap->timer_capacity * 3 / 2);
+    heap->timers =
+        gpr_realloc(heap->timers, heap->timer_capacity * sizeof(grpc_timer *));
+  }
+  timer->heap_index = heap->timer_count;
+  adjust_upwards(heap->timers, heap->timer_count, timer);
+  heap->timer_count++;
+  return timer->heap_index == 0;
+}
+
+void grpc_timer_heap_remove(grpc_timer_heap *heap, grpc_timer *timer) {
+  uint32_t i = timer->heap_index;
+  if (i == heap->timer_count - 1) {
+    heap->timer_count--;
+    maybe_shrink(heap);
+    return;
+  }
+  heap->timers[i] = heap->timers[heap->timer_count - 1];
+  heap->timers[i]->heap_index = i;
+  heap->timer_count--;
+  maybe_shrink(heap);
+  note_changed_priority(heap, heap->timers[i]);
+}
+
+int grpc_timer_heap_is_empty(grpc_timer_heap *heap) {
+  return heap->timer_count == 0;
+}
+
+grpc_timer *grpc_timer_heap_top(grpc_timer_heap *heap) {
+  return heap->timers[0];
+}
+
+void grpc_timer_heap_pop(grpc_timer_heap *heap) {
+  grpc_timer_heap_remove(heap, grpc_timer_heap_top(heap));
+}
diff --git a/src/core/lib/iomgr/timer_heap.h b/src/core/lib/iomgr/timer_heap.h
new file mode 100644
index 0000000000..d5112cf0de
--- /dev/null
+++ b/src/core/lib/iomgr/timer_heap.h
@@ -0,0 +1,57 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_TIMER_HEAP_H
+#define GRPC_CORE_LIB_IOMGR_TIMER_HEAP_H
+
+#include "src/core/lib/iomgr/timer.h"
+
+typedef struct {
+  grpc_timer **timers;
+  uint32_t timer_count;
+  uint32_t timer_capacity;
+} grpc_timer_heap;
+
+/* return 1 if the new timer is the first timer in the heap */
+int grpc_timer_heap_add(grpc_timer_heap *heap, grpc_timer *timer);
+
+void grpc_timer_heap_init(grpc_timer_heap *heap);
+void grpc_timer_heap_destroy(grpc_timer_heap *heap);
+
+void grpc_timer_heap_remove(grpc_timer_heap *heap, grpc_timer *timer);
+grpc_timer *grpc_timer_heap_top(grpc_timer_heap *heap);
+void grpc_timer_heap_pop(grpc_timer_heap *heap);
+
+int grpc_timer_heap_is_empty(grpc_timer_heap *heap);
+
+#endif /* GRPC_CORE_LIB_IOMGR_TIMER_HEAP_H */
diff --git a/src/core/lib/iomgr/udp_server.c b/src/core/lib/iomgr/udp_server.c
new file mode 100644
index 0000000000..deab40ef82
--- /dev/null
+++ b/src/core/lib/iomgr/udp_server.c
@@ -0,0 +1,416 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/* FIXME: "posix" files shouldn't be depending on _GNU_SOURCE */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GRPC_NEED_UDP
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/udp_server.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <grpc/grpc.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/time.h>
+#include "src/core/lib/iomgr/ev_posix.h"
+#include "src/core/lib/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+#include "src/core/lib/support/string.h"
+
+#define INIT_PORT_CAP 2
+
+/* one listening port */
+typedef struct {
+  int fd;
+  grpc_fd *emfd;
+  grpc_udp_server *server;
+  union {
+    uint8_t untyped[GRPC_MAX_SOCKADDR_SIZE];
+    struct sockaddr sockaddr;
+  } addr;
+  size_t addr_len;
+  grpc_closure read_closure;
+  grpc_closure destroyed_closure;
+  grpc_udp_server_read_cb read_cb;
+} server_port;
+
+/* the overall server */
+struct grpc_udp_server {
+  gpr_mu mu;
+  gpr_cv cv;
+
+  /* active port count: how many ports are actually still listening */
+  size_t active_ports;
+  /* destroyed port count: how many ports are completely destroyed */
+  size_t destroyed_ports;
+
+  /* is this server shutting down? (boolean) */
+  int shutdown;
+
+  /* all listening ports */
+  server_port *ports;
+  size_t nports;
+  size_t port_capacity;
+
+  /* shutdown callback */
+  grpc_closure *shutdown_complete;
+
+  /* all pollsets interested in new connections */
+  grpc_pollset **pollsets;
+  /* number of pollsets in the pollsets array */
+  size_t pollset_count;
+  /* The parent grpc server */
+  grpc_server *grpc_server;
+};
+
+grpc_udp_server *grpc_udp_server_create(void) {
+  grpc_udp_server *s = gpr_malloc(sizeof(grpc_udp_server));
+  gpr_mu_init(&s->mu);
+  gpr_cv_init(&s->cv);
+  s->active_ports = 0;
+  s->destroyed_ports = 0;
+  s->shutdown = 0;
+  s->ports = gpr_malloc(sizeof(server_port) * INIT_PORT_CAP);
+  s->nports = 0;
+  s->port_capacity = INIT_PORT_CAP;
+
+  return s;
+}
+
+static void finish_shutdown(grpc_exec_ctx *exec_ctx, grpc_udp_server *s) {
+  grpc_exec_ctx_enqueue(exec_ctx, s->shutdown_complete, 1, NULL);
+
+  gpr_mu_destroy(&s->mu);
+  gpr_cv_destroy(&s->cv);
+
+  gpr_free(s->ports);
+  gpr_free(s);
+}
+
+static void destroyed_port(grpc_exec_ctx *exec_ctx, void *server,
+                           bool success) {
+  grpc_udp_server *s = server;
+  gpr_mu_lock(&s->mu);
+  s->destroyed_ports++;
+  if (s->destroyed_ports == s->nports) {
+    gpr_mu_unlock(&s->mu);
+    finish_shutdown(exec_ctx, s);
+  } else {
+    gpr_mu_unlock(&s->mu);
+  }
+}
+
+/* called when all listening endpoints have been shutdown, so no further
+   events will be received on them - at this point it's safe to destroy
+   things */
+static void deactivated_all_ports(grpc_exec_ctx *exec_ctx, grpc_udp_server *s) {
+  size_t i;
+
+  /* delete ALL the things */
+  gpr_mu_lock(&s->mu);
+
+  if (!s->shutdown) {
+    gpr_mu_unlock(&s->mu);
+    return;
+  }
+
+  if (s->nports) {
+    for (i = 0; i < s->nports; i++) {
+      server_port *sp = &s->ports[i];
+      grpc_unlink_if_unix_domain_socket(&sp->addr.sockaddr);
+      sp->destroyed_closure.cb = destroyed_port;
+      sp->destroyed_closure.cb_arg = s;
+      grpc_fd_orphan(exec_ctx, sp->emfd, &sp->destroyed_closure, NULL,
+                     "udp_listener_shutdown");
+    }
+    gpr_mu_unlock(&s->mu);
+  } else {
+    gpr_mu_unlock(&s->mu);
+    finish_shutdown(exec_ctx, s);
+  }
+}
+
+void grpc_udp_server_destroy(grpc_exec_ctx *exec_ctx, grpc_udp_server *s,
+                             grpc_closure *on_done) {
+  size_t i;
+  gpr_mu_lock(&s->mu);
+
+  GPR_ASSERT(!s->shutdown);
+  s->shutdown = 1;
+
+  s->shutdown_complete = on_done;
+
+  /* shutdown all fd's */
+  if (s->active_ports) {
+    for (i = 0; i < s->nports; i++) {
+      grpc_fd_shutdown(exec_ctx, s->ports[i].emfd);
+    }
+    gpr_mu_unlock(&s->mu);
+  } else {
+    gpr_mu_unlock(&s->mu);
+    deactivated_all_ports(exec_ctx, s);
+  }
+}
+
+/* Prepare a recently-created socket for listening. */
+static int prepare_socket(int fd, const struct sockaddr *addr,
+                          size_t addr_len) {
+  struct sockaddr_storage sockname_temp;
+  socklen_t sockname_len;
+  int get_local_ip;
+  int rc;
+
+  if (fd < 0) {
+    goto error;
+  }
+
+  if (!grpc_set_socket_nonblocking(fd, 1) || !grpc_set_socket_cloexec(fd, 1)) {
+    gpr_log(GPR_ERROR, "Unable to configure socket %d: %s", fd,
+            strerror(errno));
+  }
+
+  get_local_ip = 1;
+  rc = setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &get_local_ip,
+                  sizeof(get_local_ip));
+  if (rc == 0 && addr->sa_family == AF_INET6) {
+#if !defined(__APPLE__)
+    rc = setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &get_local_ip,
+                    sizeof(get_local_ip));
+#endif
+  }
+
+  GPR_ASSERT(addr_len < ~(socklen_t)0);
+  if (bind(fd, addr, (socklen_t)addr_len) < 0) {
+    char *addr_str;
+    grpc_sockaddr_to_string(&addr_str, addr, 0);
+    gpr_log(GPR_ERROR, "bind addr=%s: %s", addr_str, strerror(errno));
+    gpr_free(addr_str);
+    goto error;
+  }
+
+  sockname_len = sizeof(sockname_temp);
+  if (getsockname(fd, (struct sockaddr *)&sockname_temp, &sockname_len) < 0) {
+    goto error;
+  }
+
+  return grpc_sockaddr_get_port((struct sockaddr *)&sockname_temp);
+
+error:
+  if (fd >= 0) {
+    close(fd);
+  }
+  return -1;
+}
+
+/* event manager callback when reads are ready */
+static void on_read(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
+  server_port *sp = arg;
+
+  if (!success) {
+    gpr_mu_lock(&sp->server->mu);
+    if (0 == --sp->server->active_ports) {
+      gpr_mu_unlock(&sp->server->mu);
+      deactivated_all_ports(exec_ctx, sp->server);
+    } else {
+      gpr_mu_unlock(&sp->server->mu);
+    }
+    return;
+  }
+
+  /* Tell the registered callback that data is available to read. */
+  GPR_ASSERT(sp->read_cb);
+  sp->read_cb(exec_ctx, sp->emfd, sp->server->grpc_server);
+
+  /* Re-arm the notification event so we get another chance to read. */
+  grpc_fd_notify_on_read(exec_ctx, sp->emfd, &sp->read_closure);
+}
+
+static int add_socket_to_server(grpc_udp_server *s, int fd,
+                                const struct sockaddr *addr, size_t addr_len,
+                                grpc_udp_server_read_cb read_cb) {
+  server_port *sp;
+  int port;
+  char *addr_str;
+  char *name;
+
+  port = prepare_socket(fd, addr, addr_len);
+  if (port >= 0) {
+    grpc_sockaddr_to_string(&addr_str, (struct sockaddr *)&addr, 1);
+    gpr_asprintf(&name, "udp-server-listener:%s", addr_str);
+    gpr_free(addr_str);
+    gpr_mu_lock(&s->mu);
+    /* append it to the list under a lock */
+    if (s->nports == s->port_capacity) {
+      s->port_capacity *= 2;
+      s->ports = gpr_realloc(s->ports, sizeof(server_port) * s->port_capacity);
+    }
+    sp = &s->ports[s->nports++];
+    sp->server = s;
+    sp->fd = fd;
+    sp->emfd = grpc_fd_create(fd, name);
+    memcpy(sp->addr.untyped, addr, addr_len);
+    sp->addr_len = addr_len;
+    sp->read_cb = read_cb;
+    GPR_ASSERT(sp->emfd);
+    gpr_mu_unlock(&s->mu);
+    gpr_free(name);
+  }
+
+  return port;
+}
+
+int grpc_udp_server_add_port(grpc_udp_server *s, const void *addr,
+                             size_t addr_len, grpc_udp_server_read_cb read_cb) {
+  int allocated_port1 = -1;
+  int allocated_port2 = -1;
+  unsigned i;
+  int fd;
+  grpc_dualstack_mode dsmode;
+  struct sockaddr_in6 addr6_v4mapped;
+  struct sockaddr_in wild4;
+  struct sockaddr_in6 wild6;
+  struct sockaddr_in addr4_copy;
+  struct sockaddr *allocated_addr = NULL;
+  struct sockaddr_storage sockname_temp;
+  socklen_t sockname_len;
+  int port;
+
+  grpc_unlink_if_unix_domain_socket((struct sockaddr *)addr);
+
+  /* Check if this is a wildcard port, and if so, try to keep the port the same
+     as some previously created listener. */
+  if (grpc_sockaddr_get_port(addr) == 0) {
+    for (i = 0; i < s->nports; i++) {
+      sockname_len = sizeof(sockname_temp);
+      if (0 == getsockname(s->ports[i].fd, (struct sockaddr *)&sockname_temp,
+                           &sockname_len)) {
+        port = grpc_sockaddr_get_port((struct sockaddr *)&sockname_temp);
+        if (port > 0) {
+          allocated_addr = malloc(addr_len);
+          memcpy(allocated_addr, addr, addr_len);
+          grpc_sockaddr_set_port(allocated_addr, port);
+          addr = allocated_addr;
+          break;
+        }
+      }
+    }
+  }
+
+  if (grpc_sockaddr_to_v4mapped(addr, &addr6_v4mapped)) {
+    addr = (const struct sockaddr *)&addr6_v4mapped;
+    addr_len = sizeof(addr6_v4mapped);
+  }
+
+  /* Treat :: or 0.0.0.0 as a family-agnostic wildcard. */
+  if (grpc_sockaddr_is_wildcard(addr, &port)) {
+    grpc_sockaddr_make_wildcards(port, &wild4, &wild6);
+
+    /* Try listening on IPv6 first. */
+    addr = (struct sockaddr *)&wild6;
+    addr_len = sizeof(wild6);
+    fd = grpc_create_dualstack_socket(addr, SOCK_DGRAM, IPPROTO_UDP, &dsmode);
+    allocated_port1 = add_socket_to_server(s, fd, addr, addr_len, read_cb);
+    if (fd >= 0 && dsmode == GRPC_DSMODE_DUALSTACK) {
+      goto done;
+    }
+
+    /* If we didn't get a dualstack socket, also listen on 0.0.0.0. */
+    if (port == 0 && allocated_port1 > 0) {
+      grpc_sockaddr_set_port((struct sockaddr *)&wild4, allocated_port1);
+    }
+    addr = (struct sockaddr *)&wild4;
+    addr_len = sizeof(wild4);
+  }
+
+  fd = grpc_create_dualstack_socket(addr, SOCK_DGRAM, IPPROTO_UDP, &dsmode);
+  if (fd < 0) {
+    gpr_log(GPR_ERROR, "Unable to create socket: %s", strerror(errno));
+  }
+  if (dsmode == GRPC_DSMODE_IPV4 &&
+      grpc_sockaddr_is_v4mapped(addr, &addr4_copy)) {
+    addr = (struct sockaddr *)&addr4_copy;
+    addr_len = sizeof(addr4_copy);
+  }
+  allocated_port2 = add_socket_to_server(s, fd, addr, addr_len, read_cb);
+
+done:
+  gpr_free(allocated_addr);
+  return allocated_port1 >= 0 ? allocated_port1 : allocated_port2;
+}
+
+int grpc_udp_server_get_fd(grpc_udp_server *s, unsigned port_index) {
+  return (port_index < s->nports) ? s->ports[port_index].fd : -1;
+}
+
+void grpc_udp_server_start(grpc_exec_ctx *exec_ctx, grpc_udp_server *s,
+                           grpc_pollset **pollsets, size_t pollset_count,
+                           grpc_server *server) {
+  size_t i, j;
+  gpr_mu_lock(&s->mu);
+  GPR_ASSERT(s->active_ports == 0);
+  s->pollsets = pollsets;
+  s->grpc_server = server;
+  for (i = 0; i < s->nports; i++) {
+    for (j = 0; j < pollset_count; j++) {
+      grpc_pollset_add_fd(exec_ctx, pollsets[j], s->ports[i].emfd);
+    }
+    s->ports[i].read_closure.cb = on_read;
+    s->ports[i].read_closure.cb_arg = &s->ports[i];
+    grpc_fd_notify_on_read(exec_ctx, s->ports[i].emfd,
+                           &s->ports[i].read_closure);
+    s->active_ports++;
+  }
+  gpr_mu_unlock(&s->mu);
+}
+
+#endif
+#endif
diff --git a/src/core/lib/iomgr/udp_server.h b/src/core/lib/iomgr/udp_server.h
new file mode 100644
index 0000000000..f3fb0c59f0
--- /dev/null
+++ b/src/core/lib/iomgr/udp_server.h
@@ -0,0 +1,77 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_UDP_SERVER_H
+#define GRPC_CORE_LIB_IOMGR_UDP_SERVER_H
+
+#include "src/core/lib/iomgr/endpoint.h"
+#include "src/core/lib/iomgr/ev_posix.h"
+
+/* Forward decl of struct grpc_server */
+/* This is not typedef'ed to avoid a typedef-redefinition error */
+struct grpc_server;
+
+/* Forward decl of grpc_udp_server */
+typedef struct grpc_udp_server grpc_udp_server;
+
+/* Called when data is available to read from the socket. */
+typedef void (*grpc_udp_server_read_cb)(grpc_exec_ctx *exec_ctx, grpc_fd *emfd,
+                                        struct grpc_server *server);
+
+/* Create a server, initially not bound to any ports */
+grpc_udp_server *grpc_udp_server_create(void);
+
+/* Start listening to bound ports */
+void grpc_udp_server_start(grpc_exec_ctx *exec_ctx, grpc_udp_server *udp_server,
+                           grpc_pollset **pollsets, size_t pollset_count,
+                           struct grpc_server *server);
+
+int grpc_udp_server_get_fd(grpc_udp_server *s, unsigned index);
+
+/* Add a port to the server, returning port number on success, or negative
+   on failure.
+
+   The :: and 0.0.0.0 wildcard addresses are treated identically, accepting
+   both IPv4 and IPv6 connections, but :: is the preferred style.  This usually
+   creates one socket, but possibly two on systems which support IPv6,
+   but not dualstack sockets. */
+
+/* TODO(ctiller): deprecate this, and make grpc_udp_server_add_ports to handle
+                  all of the multiple socket port matching logic in one place */
+int grpc_udp_server_add_port(grpc_udp_server *s, const void *addr,
+                             size_t addr_len, grpc_udp_server_read_cb read_cb);
+
+void grpc_udp_server_destroy(grpc_exec_ctx *exec_ctx, grpc_udp_server *server,
+                             grpc_closure *on_done);
+
+#endif /* GRPC_CORE_LIB_IOMGR_UDP_SERVER_H */
diff --git a/src/core/lib/iomgr/unix_sockets_posix.c b/src/core/lib/iomgr/unix_sockets_posix.c
new file mode 100644
index 0000000000..42e44989e0
--- /dev/null
+++ b/src/core/lib/iomgr/unix_sockets_posix.c
@@ -0,0 +1,103 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+
+#ifdef GPR_HAVE_UNIX_SOCKET
+
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/un.h>
+
+#include <grpc/support/alloc.h>
+
+void grpc_create_socketpair_if_unix(int sv[2]) {
+  GPR_ASSERT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == 0);
+}
+
+grpc_resolved_addresses *grpc_resolve_unix_domain_address(const char *name) {
+  struct sockaddr_un *un;
+
+  grpc_resolved_addresses *addrs = gpr_malloc(sizeof(grpc_resolved_addresses));
+  addrs->naddrs = 1;
+  addrs->addrs = gpr_malloc(sizeof(grpc_resolved_address));
+  un = (struct sockaddr_un *)addrs->addrs->addr;
+  un->sun_family = AF_UNIX;
+  strcpy(un->sun_path, name);
+  addrs->addrs->len = strlen(un->sun_path) + sizeof(un->sun_family) + 1;
+  return addrs;
+}
+
+int grpc_is_unix_socket(const struct sockaddr *addr) {
+  return addr->sa_family == AF_UNIX;
+}
+
+void grpc_unlink_if_unix_domain_socket(const struct sockaddr *addr) {
+  if (addr->sa_family != AF_UNIX) {
+    return;
+  }
+  struct sockaddr_un *un = (struct sockaddr_un *)addr;
+  struct stat st;
+
+  if (stat(un->sun_path, &st) == 0 && (st.st_mode & S_IFMT) == S_IFSOCK) {
+    unlink(un->sun_path);
+  }
+}
+
+int grpc_parse_unix(grpc_uri *uri, struct sockaddr_storage *addr, size_t *len) {
+  struct sockaddr_un *un = (struct sockaddr_un *)addr;
+
+  un->sun_family = AF_UNIX;
+  strcpy(un->sun_path, uri->path);
+  *len = strlen(un->sun_path) + sizeof(un->sun_family) + 1;
+
+  return 1;
+}
+
+char *grpc_unix_get_default_authority(grpc_resolver_factory *factory,
+                                      grpc_uri *uri) {
+  return gpr_strdup("localhost");
+}
+
+char *grpc_sockaddr_to_uri_unix_if_possible(const struct sockaddr *addr) {
+  if (addr->sa_family != AF_UNIX) {
+    return NULL;
+  }
+
+  char *result;
+  gpr_asprintf(&result, "unix:%s", ((struct sockaddr_un *)addr)->sun_path);
+  return result;
+}
+
+#endif
diff --git a/src/core/lib/iomgr/unix_sockets_posix.h b/src/core/lib/iomgr/unix_sockets_posix.h
new file mode 100644
index 0000000000..752cab85a5
--- /dev/null
+++ b/src/core/lib/iomgr/unix_sockets_posix.h
@@ -0,0 +1,61 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_UNIX_SOCKETS_POSIX_H
+#define GRPC_CORE_LIB_IOMGR_UNIX_SOCKETS_POSIX_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/client_config/resolver_factory.h"
+#include "src/core/lib/client_config/uri_parser.h"
+#include "src/core/lib/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+
+void grpc_create_socketpair_if_unix(int sv[2]);
+
+grpc_resolved_addresses *grpc_resolve_unix_domain_address(const char *name);
+
+int grpc_is_unix_socket(const struct sockaddr *addr);
+
+void grpc_unlink_if_unix_domain_socket(const struct sockaddr *addr);
+
+int grpc_parse_unix(grpc_uri *uri, struct sockaddr_storage *addr, size_t *len);
+
+char *grpc_unix_get_default_authority(grpc_resolver_factory *factory,
+                                      grpc_uri *uri);
+
+char *grpc_sockaddr_to_uri_unix_if_possible(const struct sockaddr *addr);
+
+#endif /* GRPC_CORE_LIB_IOMGR_UNIX_SOCKETS_POSIX_H */
diff --git a/src/core/lib/iomgr/unix_sockets_posix_noop.c b/src/core/lib/iomgr/unix_sockets_posix_noop.c
new file mode 100644
index 0000000000..06f6ee05e7
--- /dev/null
+++ b/src/core/lib/iomgr/unix_sockets_posix_noop.c
@@ -0,0 +1,61 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+
+#ifndef GPR_HAVE_UNIX_SOCKET
+
+void grpc_create_socketpair_if_unix(int sv[2]) {}
+
+grpc_resolved_addresses *grpc_resolve_unix_domain_address(const char *name) {
+  return NULL;
+}
+
+int grpc_is_unix_socket(const struct sockaddr *addr) { return false; }
+
+void grpc_unlink_if_unix_domain_socket(const struct sockaddr *addr) {}
+
+int grpc_parse_unix(grpc_uri *uri, struct sockaddr_storage *addr, size_t *len) {
+  return 0;
+}
+
+char *grpc_unix_get_default_authority(grpc_resolver_factory *factory,
+                                      grpc_uri *uri) {
+  return NULL;
+}
+
+char *grpc_sockaddr_to_uri_unix_if_possible(const struct sockaddr *addr) {
+  return NULL;
+}
+
+#endif
diff --git a/src/core/lib/iomgr/wakeup_fd_eventfd.c b/src/core/lib/iomgr/wakeup_fd_eventfd.c
new file mode 100644
index 0000000000..41ded0ca4d
--- /dev/null
+++ b/src/core/lib/iomgr/wakeup_fd_eventfd.c
@@ -0,0 +1,85 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_LINUX_EVENTFD
+
+#include <errno.h>
+#include <sys/eventfd.h>
+#include <unistd.h>
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+#include "src/core/lib/profiling/timers.h"
+
+static void eventfd_create(grpc_wakeup_fd* fd_info) {
+  int efd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+  /* TODO(klempner): Handle failure more gracefully */
+  GPR_ASSERT(efd >= 0);
+  fd_info->read_fd = efd;
+  fd_info->write_fd = -1;
+}
+
+static void eventfd_consume(grpc_wakeup_fd* fd_info) {
+  eventfd_t value;
+  int err;
+  do {
+    err = eventfd_read(fd_info->read_fd, &value);
+  } while (err < 0 && errno == EINTR);
+}
+
+static void eventfd_wakeup(grpc_wakeup_fd* fd_info) {
+  int err;
+  GPR_TIMER_BEGIN("eventfd_wakeup", 0);
+  do {
+    err = eventfd_write(fd_info->read_fd, 1);
+  } while (err < 0 && errno == EINTR);
+  GPR_TIMER_END("eventfd_wakeup", 0);
+}
+
+static void eventfd_destroy(grpc_wakeup_fd* fd_info) {
+  if (fd_info->read_fd != 0) close(fd_info->read_fd);
+}
+
+static int eventfd_check_availability(void) {
+  /* TODO(klempner): Actually check if eventfd is available */
+  return 1;
+}
+
+const grpc_wakeup_fd_vtable grpc_specialized_wakeup_fd_vtable = {
+    eventfd_create, eventfd_consume, eventfd_wakeup, eventfd_destroy,
+    eventfd_check_availability};
+
+#endif /* GPR_LINUX_EVENTFD */
diff --git a/src/core/lib/iomgr/wakeup_fd_nospecial.c b/src/core/lib/iomgr/wakeup_fd_nospecial.c
new file mode 100644
index 0000000000..39defa65c6
--- /dev/null
+++ b/src/core/lib/iomgr/wakeup_fd_nospecial.c
@@ -0,0 +1,51 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/*
+ * This is a dummy file to provide an invalid specialized_wakeup_fd_vtable on
+ * systems without anything better than pipe.
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_NO_SPECIAL_WAKEUP_FD
+
+#include <stddef.h>
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+
+static int check_availability_invalid(void) { return 0; }
+
+const grpc_wakeup_fd_vtable grpc_specialized_wakeup_fd_vtable = {
+    NULL, NULL, NULL, NULL, check_availability_invalid};
+
+#endif /* GPR_POSIX_NO_SPECIAL_WAKEUP_FD */
diff --git a/src/core/lib/iomgr/wakeup_fd_pipe.c b/src/core/lib/iomgr/wakeup_fd_pipe.c
new file mode 100644
index 0000000000..820919e4dd
--- /dev/null
+++ b/src/core/lib/iomgr/wakeup_fd_pipe.c
@@ -0,0 +1,102 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_WAKEUP_FD
+
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+
+static void pipe_init(grpc_wakeup_fd* fd_info) {
+  int pipefd[2];
+  /* TODO(klempner): Make this nonfatal */
+  int r = pipe(pipefd);
+  if (0 != r) {
+    gpr_log(GPR_ERROR, "pipe creation failed (%d): %s", errno, strerror(errno));
+    abort();
+  }
+  GPR_ASSERT(grpc_set_socket_nonblocking(pipefd[0], 1));
+  GPR_ASSERT(grpc_set_socket_nonblocking(pipefd[1], 1));
+  fd_info->read_fd = pipefd[0];
+  fd_info->write_fd = pipefd[1];
+}
+
+static void pipe_consume(grpc_wakeup_fd* fd_info) {
+  char buf[128];
+  ssize_t r;
+
+  for (;;) {
+    r = read(fd_info->read_fd, buf, sizeof(buf));
+    if (r > 0) continue;
+    if (r == 0) return;
+    switch (errno) {
+      case EAGAIN:
+        return;
+      case EINTR:
+        continue;
+      default:
+        gpr_log(GPR_ERROR, "error reading pipe: %s", strerror(errno));
+        return;
+    }
+  }
+}
+
+static void pipe_wakeup(grpc_wakeup_fd* fd_info) {
+  char c = 0;
+  while (write(fd_info->write_fd, &c, 1) != 1 && errno == EINTR)
+    ;
+}
+
+static void pipe_destroy(grpc_wakeup_fd* fd_info) {
+  if (fd_info->read_fd != 0) close(fd_info->read_fd);
+  if (fd_info->write_fd != 0) close(fd_info->write_fd);
+}
+
+static int pipe_check_availability(void) {
+  /* Assume that pipes are always available. */
+  return 1;
+}
+
+const grpc_wakeup_fd_vtable grpc_pipe_wakeup_fd_vtable = {
+    pipe_init, pipe_consume, pipe_wakeup, pipe_destroy,
+    pipe_check_availability};
+
+#endif /* GPR_POSIX_WAKUP_FD */
diff --git a/src/core/lib/iomgr/wakeup_fd_pipe.h b/src/core/lib/iomgr/wakeup_fd_pipe.h
new file mode 100644
index 0000000000..bbdb1fc448
--- /dev/null
+++ b/src/core/lib/iomgr/wakeup_fd_pipe.h
@@ -0,0 +1,41 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_WAKEUP_FD_PIPE_H
+#define GRPC_CORE_LIB_IOMGR_WAKEUP_FD_PIPE_H
+
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+
+extern grpc_wakeup_fd_vtable grpc_pipe_wakeup_fd_vtable;
+
+#endif /* GRPC_CORE_LIB_IOMGR_WAKEUP_FD_PIPE_H */
diff --git a/src/core/lib/iomgr/wakeup_fd_posix.c b/src/core/lib/iomgr/wakeup_fd_posix.c
new file mode 100644
index 0000000000..c4d174fb34
--- /dev/null
+++ b/src/core/lib/iomgr/wakeup_fd_posix.c
@@ -0,0 +1,72 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_WAKEUP_FD
+
+#include <stddef.h>
+#include "src/core/lib/iomgr/wakeup_fd_pipe.h"
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+
+static const grpc_wakeup_fd_vtable *wakeup_fd_vtable = NULL;
+int grpc_allow_specialized_wakeup_fd = 1;
+
+void grpc_wakeup_fd_global_init(void) {
+  if (grpc_allow_specialized_wakeup_fd &&
+      grpc_specialized_wakeup_fd_vtable.check_availability()) {
+    wakeup_fd_vtable = &grpc_specialized_wakeup_fd_vtable;
+  } else {
+    wakeup_fd_vtable = &grpc_pipe_wakeup_fd_vtable;
+  }
+}
+
+void grpc_wakeup_fd_global_destroy(void) { wakeup_fd_vtable = NULL; }
+
+void grpc_wakeup_fd_init(grpc_wakeup_fd *fd_info) {
+  wakeup_fd_vtable->init(fd_info);
+}
+
+void grpc_wakeup_fd_consume_wakeup(grpc_wakeup_fd *fd_info) {
+  wakeup_fd_vtable->consume(fd_info);
+}
+
+void grpc_wakeup_fd_wakeup(grpc_wakeup_fd *fd_info) {
+  wakeup_fd_vtable->wakeup(fd_info);
+}
+
+void grpc_wakeup_fd_destroy(grpc_wakeup_fd *fd_info) {
+  wakeup_fd_vtable->destroy(fd_info);
+}
+
+#endif /* GPR_POSIX_WAKEUP_FD */
diff --git a/src/core/lib/iomgr/wakeup_fd_posix.h b/src/core/lib/iomgr/wakeup_fd_posix.h
new file mode 100644
index 0000000000..20988d5fd3
--- /dev/null
+++ b/src/core/lib/iomgr/wakeup_fd_posix.h
@@ -0,0 +1,101 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/*
+ * wakeup_fd abstracts the concept of a file descriptor for the purpose of
+ * waking up a thread in select()/poll()/epoll_wait()/etc.
+
+ * The poll() family of system calls provide a way for a thread to block until
+ * there is activity on one (or more) of a set of file descriptors. An
+ * application may wish to wake up this thread to do non file related work. The
+ * typical way to do this is to add a pipe to the set of file descriptors, then
+ * write to the pipe to wake up the thread in poll().
+ *
+ * Linux has a lighter weight eventfd specifically designed for this purpose.
+ * wakeup_fd abstracts the difference between the two.
+ *
+ * Setup:
+ * 1. Before calling anything, call global_init() at least once.
+ * 1. Call grpc_wakeup_fd_create() to get a wakeup_fd.
+ * 2. Add the result of GRPC_WAKEUP_FD_FD to the set of monitored file
+ *    descriptors for the poll() style API you are using. Monitor the file
+ *    descriptor for readability.
+ * 3. To tear down, call grpc_wakeup_fd_destroy(). This closes the underlying
+ *    file descriptor.
+ *
+ * Usage:
+ * 1. To wake up a polling thread, call grpc_wakeup_fd_wakeup() on a wakeup_fd
+ *    it is monitoring.
+ * 2. If the polling thread was awakened by a wakeup_fd event, call
+ *    grpc_wakeup_fd_consume_wakeup() on it.
+ */
+#ifndef GRPC_CORE_LIB_IOMGR_WAKEUP_FD_POSIX_H
+#define GRPC_CORE_LIB_IOMGR_WAKEUP_FD_POSIX_H
+
+void grpc_wakeup_fd_global_init(void);
+void grpc_wakeup_fd_global_destroy(void);
+
+/* Force using the fallback implementation. This is intended for testing
+ * purposes only.*/
+void grpc_wakeup_fd_global_init_force_fallback(void);
+
+typedef struct grpc_wakeup_fd grpc_wakeup_fd;
+
+typedef struct grpc_wakeup_fd_vtable {
+  void (*init)(grpc_wakeup_fd* fd_info);
+  void (*consume)(grpc_wakeup_fd* fd_info);
+  void (*wakeup)(grpc_wakeup_fd* fd_info);
+  void (*destroy)(grpc_wakeup_fd* fd_info);
+  /* Must be called before calling any other functions */
+  int (*check_availability)(void);
+} grpc_wakeup_fd_vtable;
+
+struct grpc_wakeup_fd {
+  int read_fd;
+  int write_fd;
+};
+
+extern int grpc_allow_specialized_wakeup_fd;
+
+#define GRPC_WAKEUP_FD_GET_READ_FD(fd_info) ((fd_info)->read_fd)
+
+void grpc_wakeup_fd_init(grpc_wakeup_fd* fd_info);
+void grpc_wakeup_fd_consume_wakeup(grpc_wakeup_fd* fd_info);
+void grpc_wakeup_fd_wakeup(grpc_wakeup_fd* fd_info);
+void grpc_wakeup_fd_destroy(grpc_wakeup_fd* fd_info);
+
+/* Defined in some specialized implementation's .c file, or by
+ * wakeup_fd_nospecial.c if no such implementation exists. */
+extern const grpc_wakeup_fd_vtable grpc_specialized_wakeup_fd_vtable;
+
+#endif /* GRPC_CORE_LIB_IOMGR_WAKEUP_FD_POSIX_H */
diff --git a/src/core/lib/iomgr/workqueue.h b/src/core/lib/iomgr/workqueue.h
new file mode 100644
index 0000000000..9c420c57de
--- /dev/null
+++ b/src/core/lib/iomgr/workqueue.h
@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_WORKQUEUE_H
+#define GRPC_CORE_LIB_IOMGR_WORKQUEUE_H
+
+#include "src/core/lib/iomgr/closure.h"
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/iomgr.h"
+#include "src/core/lib/iomgr/pollset.h"
+
+#ifdef GPR_POSIX_SOCKET
+#include "src/core/lib/iomgr/workqueue_posix.h"
+#endif
+
+#ifdef GPR_WIN32
+#include "src/core/lib/iomgr/workqueue_windows.h"
+#endif
+
+/* grpc_workqueue is forward declared in exec_ctx.h */
+
+/** Create a work queue */
+grpc_workqueue *grpc_workqueue_create(grpc_exec_ctx *exec_ctx);
+
+void grpc_workqueue_flush(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
+
+#define GRPC_WORKQUEUE_REFCOUNT_DEBUG
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+#define GRPC_WORKQUEUE_REF(p, r) \
+  grpc_workqueue_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_WORKQUEUE_UNREF(cl, p, r) \
+  grpc_workqueue_unref((cl), (p), __FILE__, __LINE__, (r))
+void grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file, int line,
+                        const char *reason);
+void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                          const char *file, int line, const char *reason);
+#else
+#define GRPC_WORKQUEUE_REF(p, r) grpc_workqueue_ref((p))
+#define GRPC_WORKQUEUE_UNREF(cl, p, r) grpc_workqueue_unref((cl), (p))
+void grpc_workqueue_ref(grpc_workqueue *workqueue);
+void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
+#endif
+
+/** Bind this workqueue to a pollset */
+void grpc_workqueue_add_to_pollset(grpc_exec_ctx *exec_ctx,
+                                   grpc_workqueue *workqueue,
+                                   grpc_pollset *pollset);
+
+/** Add a work item to a workqueue */
+void grpc_workqueue_push(grpc_workqueue *workqueue, grpc_closure *closure,
+                         int success);
+
+#endif /* GRPC_CORE_LIB_IOMGR_WORKQUEUE_H */
diff --git a/src/core/lib/iomgr/workqueue_posix.c b/src/core/lib/iomgr/workqueue_posix.c
new file mode 100644
index 0000000000..08c48b8c35
--- /dev/null
+++ b/src/core/lib/iomgr/workqueue_posix.c
@@ -0,0 +1,143 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_SOCKET
+
+#include "src/core/lib/iomgr/workqueue.h"
+
+#include <stdio.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/useful.h>
+
+#include "src/core/lib/iomgr/ev_posix.h"
+
+static void on_readable(grpc_exec_ctx *exec_ctx, void *arg, bool success);
+
+grpc_workqueue *grpc_workqueue_create(grpc_exec_ctx *exec_ctx) {
+  char name[32];
+  grpc_workqueue *workqueue = gpr_malloc(sizeof(grpc_workqueue));
+  gpr_ref_init(&workqueue->refs, 1);
+  gpr_mu_init(&workqueue->mu);
+  workqueue->closure_list.head = workqueue->closure_list.tail = NULL;
+  grpc_wakeup_fd_init(&workqueue->wakeup_fd);
+  sprintf(name, "workqueue:%p", (void *)workqueue);
+  workqueue->wakeup_read_fd =
+      grpc_fd_create(GRPC_WAKEUP_FD_GET_READ_FD(&workqueue->wakeup_fd), name);
+  grpc_closure_init(&workqueue->read_closure, on_readable, workqueue);
+  grpc_fd_notify_on_read(exec_ctx, workqueue->wakeup_read_fd,
+                         &workqueue->read_closure);
+  return workqueue;
+}
+
+static void workqueue_destroy(grpc_exec_ctx *exec_ctx,
+                              grpc_workqueue *workqueue) {
+  GPR_ASSERT(grpc_closure_list_empty(workqueue->closure_list));
+  grpc_fd_shutdown(exec_ctx, workqueue->wakeup_read_fd);
+}
+
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+void grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file, int line,
+                        const char *reason) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "WORKQUEUE:%p   ref %d -> %d %s",
+          workqueue, (int)workqueue->refs.count, (int)workqueue->refs.count + 1,
+          reason);
+#else
+void grpc_workqueue_ref(grpc_workqueue *workqueue) {
+#endif
+  gpr_ref(&workqueue->refs);
+}
+
+#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
+                          const char *file, int line, const char *reason) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "WORKQUEUE:%p unref %d -> %d %s",
+          workqueue, (int)workqueue->refs.count, (int)workqueue->refs.count - 1,
+          reason);
+#else
+void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {
+#endif
+  if (gpr_unref(&workqueue->refs)) {
+    workqueue_destroy(exec_ctx, workqueue);
+  }
+}
+
+void grpc_workqueue_add_to_pollset(grpc_exec_ctx *exec_ctx,
+                                   grpc_workqueue *workqueue,
+                                   grpc_pollset *pollset) {
+  grpc_pollset_add_fd(exec_ctx, pollset, workqueue->wakeup_read_fd);
+}
+
+void grpc_workqueue_flush(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {
+  gpr_mu_lock(&workqueue->mu);
+  if (grpc_closure_list_empty(workqueue->closure_list)) {
+    grpc_wakeup_fd_wakeup(&workqueue->wakeup_fd);
+  }
+  grpc_exec_ctx_enqueue_list(exec_ctx, &workqueue->closure_list, NULL);
+  gpr_mu_unlock(&workqueue->mu);
+}
+
+static void on_readable(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
+  grpc_workqueue *workqueue = arg;
+
+  if (!success) {
+    gpr_mu_destroy(&workqueue->mu);
+    /* HACK: let wakeup_fd code know that we stole the fd */
+    workqueue->wakeup_fd.read_fd = 0;
+    grpc_wakeup_fd_destroy(&workqueue->wakeup_fd);
+    grpc_fd_orphan(exec_ctx, workqueue->wakeup_read_fd, NULL, NULL, "destroy");
+    gpr_free(workqueue);
+  } else {
+    gpr_mu_lock(&workqueue->mu);
+    grpc_exec_ctx_enqueue_list(exec_ctx, &workqueue->closure_list, NULL);
+    grpc_wakeup_fd_consume_wakeup(&workqueue->wakeup_fd);
+    gpr_mu_unlock(&workqueue->mu);
+    grpc_fd_notify_on_read(exec_ctx, workqueue->wakeup_read_fd,
+                           &workqueue->read_closure);
+  }
+}
+
+void grpc_workqueue_push(grpc_workqueue *workqueue, grpc_closure *closure,
+                         int success) {
+  gpr_mu_lock(&workqueue->mu);
+  if (grpc_closure_list_empty(workqueue->closure_list)) {
+    grpc_wakeup_fd_wakeup(&workqueue->wakeup_fd);
+  }
+  grpc_closure_list_add(&workqueue->closure_list, closure, success);
+  gpr_mu_unlock(&workqueue->mu);
+}
+
+#endif /* GPR_POSIX_SOCKET */
diff --git a/src/core/lib/iomgr/workqueue_posix.h b/src/core/lib/iomgr/workqueue_posix.h
new file mode 100644
index 0000000000..956de8fb27
--- /dev/null
+++ b/src/core/lib/iomgr/workqueue_posix.h
@@ -0,0 +1,53 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_WORKQUEUE_POSIX_H
+#define GRPC_CORE_LIB_IOMGR_WORKQUEUE_POSIX_H
+
+#include "src/core/lib/iomgr/wakeup_fd_posix.h"
+
+struct grpc_fd;
+
+struct grpc_workqueue {
+  gpr_refcount refs;
+
+  gpr_mu mu;
+  grpc_closure_list closure_list;
+
+  grpc_wakeup_fd wakeup_fd;
+  struct grpc_fd *wakeup_read_fd;
+
+  grpc_closure read_closure;
+};
+
+#endif /* GRPC_CORE_LIB_IOMGR_WORKQUEUE_POSIX_H */
diff --git a/src/core/lib/iomgr/workqueue_windows.c b/src/core/lib/iomgr/workqueue_windows.c
new file mode 100644
index 0000000000..6697f93498
--- /dev/null
+++ b/src/core/lib/iomgr/workqueue_windows.c
@@ -0,0 +1,40 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WIN32
+
+#include "src/core/lib/iomgr/workqueue.h"
+
+#endif /* GPR_WIN32 */
diff --git a/src/core/lib/iomgr/workqueue_windows.h b/src/core/lib/iomgr/workqueue_windows.h
new file mode 100644
index 0000000000..8e6980b6d9
--- /dev/null
+++ b/src/core/lib/iomgr/workqueue_windows.h
@@ -0,0 +1,37 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_WORKQUEUE_WINDOWS_H
+#define GRPC_CORE_LIB_IOMGR_WORKQUEUE_WINDOWS_H
+
+#endif /* GRPC_CORE_LIB_IOMGR_WORKQUEUE_WINDOWS_H */