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diff --git a/examples/cpp/metadata/README.md b/examples/cpp/metadata/README.md new file mode 100644 index 0000000000..7b33074ba1 --- /dev/null +++ b/examples/cpp/metadata/README.md @@ -0,0 +1,69 @@ +# Metadata Example + +## Overview + +This example shows you how to add custom headers on the client and server and +how to access them. + +Custom metadata must follow the "Custom-Metadata" format listed in +https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md, with the +exception of binary headers, which don't have to be base64 encoded. + +### Get the tutorial source code + The example code for this and our other examples lives in the `examples` directory. Clone this repository to your local machine by running the following command: + ```sh +$ git clone -b $(curl -L https://grpc.io/release) https://github.com/grpc/grpc +``` + Change your current directory to examples/cpp/metadata + ```sh +$ cd examples/cpp/metadata +``` + +### Generating gRPC code + To generate the client and server side interfaces: + ```sh +$ make helloworld.grpc.pb.cc helloworld.pb.cc +``` +Which internally invokes the proto-compiler as: + ```sh +$ protoc -I ../../protos/ --grpc_out=. --plugin=protoc-gen-grpc=grpc_cpp_plugin ../../protos/helloworld.proto +$ protoc -I ../../protos/ --cpp_out=. ../../protos/helloworld.proto +``` +### Try it! +Build client and server: + +```sh +$ make +``` + +Run the server, which will listen on port 50051: + +```sh +$ ./greeter_server +``` + +Run the client (in a different terminal): + +```sh +$ ./greeter_client +``` + +If things go smoothly, you will see in the client terminal: + +"Client received initial metadata from server: initial metadata value" +"Client received trailing metadata from server: trailing metadata value" +"Client received message: Hello World" + + +And in the server terminal: + +"Header key: custom-bin , value: " +"Header key: custom-header , value: Custom Value" +"Header key: user-agent , value: grpc-c++/1.16.0-dev grpc-c/6.0.0-dev (linux; chttp2; gao)" + +Note that the value for custom-bin doesn't print nicely because it's a binary +value. You can indicate a binary value through appending "-bin" to the header key. + +We did not add the user-agent metadata as a custom header. This shows how +the gRPC framework adds some headers under the hood that may show up in the +metadata map. |