gRPC入门教程：Hello World

本文示例来自grpc官方源码示例。

目的

客户端向服务端请求Hello，同时发送World，服务端拼接字符串返回Hello World。

Proto

syntax = "proto3";

option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";

package helloworld;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}

  rpc SayHelloStreamReply (HelloRequest) returns (stream HelloReply) {}

  rpc SayHelloBidiStream (stream HelloRequest) returns (stream HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

服务端

#include <iostream>
#include <memory>
#include <string>

#include "absl/flags/flag.h"
#include "absl/flags/parse.h"
#include "absl/strings/str_format.h"

#include <grpcpp/ext/proto_server_reflection_plugin.h>
#include <grpcpp/grpcpp.h>
#include <grpcpp/health_check_service_interface.h>

#ifdef BAZEL_BUILD
#include "examples/protos/helloworld.grpc.pb.h"
#else
#include "helloworld.grpc.pb.h"
#endif

using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;
using helloworld::Greeter;
using helloworld::HelloReply;
using helloworld::HelloRequest;

ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");

// Logic and data behind the server's behavior.
class GreeterServiceImpl final : public Greeter::Service {
  Status SayHello(ServerContext* context, const HelloRequest* request,
                  HelloReply* reply) override {
    std::string prefix("Hello ");
    reply->set_message(prefix + request->name());
    return Status::OK;
  }
};

void RunServer(uint16_t port) {
  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
  GreeterServiceImpl service;

  grpc::EnableDefaultHealthCheckService(true);
  grpc::reflection::InitProtoReflectionServerBuilderPlugin();
  ServerBuilder builder;
  // Listen on the given address without any authentication mechanism.
  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
  // Register "service" as the instance through which we'll communicate with
  // clients. In this case it corresponds to an *synchronous* service.
  builder.RegisterService(&service);
  // Finally assemble the server.
  std::unique_ptr<Server> server(builder.BuildAndStart());
  std::cout << "Server listening on " << server_address << std::endl;

  // Wait for the server to shutdown. Note that some other thread must be
  // responsible for shutting down the server for this call to ever return.
  server->Wait();
}

int main(int argc, char** argv) {
  absl::ParseCommandLine(argc, argv);
  RunServer(absl::GetFlag(FLAGS_port));
  return 0;
}

客户端

#include <iostream>
#include <memory>
#include <string>

#include "absl/flags/flag.h"
#include "absl/flags/parse.h"

#include <grpcpp/grpcpp.h>

#ifdef BAZEL_BUILD
#include "examples/protos/helloworld.grpc.pb.h"
#else
#include "helloworld.grpc.pb.h"
#endif

ABSL_FLAG(std::string, target, "localhost:50051", "Server address");

using grpc::Channel;
using grpc::ClientContext;
using grpc::Status;
using helloworld::Greeter;
using helloworld::HelloReply;
using helloworld::HelloRequest;

class GreeterClient {
 public:
  GreeterClient(std::shared_ptr<Channel> channel)
      : stub_(Greeter::NewStub(channel)) {}

  // Assembles the client's payload, sends it and presents the response back
  // from the server.
  std::string SayHello(const std::string& user) {
    // Data we are sending to the server.
    HelloRequest request;
    request.set_name(user);

    // Container for the data we expect from the server.
    HelloReply reply;

    // Context for the client. It could be used to convey extra information to
    // the server and/or tweak certain RPC behaviors.
    ClientContext context;

    // The actual RPC.
    Status status = stub_->SayHello(&context, request, &reply);

    // Act upon its status.
    if (status.ok()) {
      return reply.message();
    } else {
      std::cout << status.error_code() << ": " << status.error_message()
                << std::endl;
      return "RPC failed";
    }
  }

 private:
  std::unique_ptr<Greeter::Stub> stub_;
};

int main(int argc, char** argv) {
  absl::ParseCommandLine(argc, argv);
  // Instantiate the client. It requires a channel, out of which the actual RPCs
  // are created. This channel models a connection to an endpoint specified by
  // the argument "--target=" which is the only expected argument.
  std::string target_str = absl::GetFlag(FLAGS_target);
  // We indicate that the channel isn't authenticated (use of
  // InsecureChannelCredentials()).
  GreeterClient greeter(
      grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
  std::string user("world");
  std::string reply = greeter.SayHello(user);
  std::cout << "Greeter received: " << reply << std::endl;

  return 0;
}

运行

编译运行服务端，输出为

hyper372@hyper372-test:~/Documents/grpc/examples/cpp/helloworld/build$ ./greeter_callback_server
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1723773102.328242    4566 config.cc:257] gRPC experiments enabled: call_status_override_on_cancellation, call_tracer_in_transport, event_engine_dns, event_engine_listener, monitoring_experiment, pick_first_new, trace_record_callops, work_serializer_clears_time_cache
I0000 00:00:1723773102.331365    4566 server_builder.cc:392] Synchronous server. Num CQs: 1, Min pollers: 1, Max Pollers: 2, CQ timeout (msec): 10000
I0000 00:00:1723773102.331432    4566 server_builder.cc:401] Callback server.
Server listening on 0.0.0.0:50051

服务端运行，监听50051端口。

运行客户端，输出为：

hyper372@hyper372-test:~/Documents/grpc/examples/cpp/helloworld/build$ ./greeter_callback_client
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1723773123.258449    4604 config.cc:257] gRPC experiments enabled: call_status_override_on_cancellation, call_tracer_in_transport, event_engine_dns, event_engine_listener, monitoring_experiment, pick_first_new, trace_record_callops, work_serializer_clears_time_cache
Greeter received: Hello world