C++ 使用gRPC入门教程

    gRPC是一个高性能、通用的开源RPC框架，其由Google主要面向移动应用开发并基于HTTP/2协议标准而设计，基于ProtoBuf(Protocol Buffers)序列化协议开发，且支持众多开发语言，能够基于语言自动生成客户端和服务端功能库。   

1.新建工程GrpcClient、GrpcServer和GrpcLibrary

   添加 - 新建项目 - 控制台应用 GrpcClient、GrpcServer。

   添加 - 新建项目 - 类库 GrpcLibrary。 工程中的三个项目情况如下：

   

2.自定义服务

    在项目GrpcLibrary里添加HelloWorld.proto用以生成代码。

syntax = "proto3";
package GrpcLibrary;

service GrpcService {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

    执行命令

ThirdParty\grpc_build\bin\protoc.exe -IGrpcLibrary --cpp_out GrpcLibrary  GrpcLibrary\HelloWorld.proto --grpc_out GrpcLibrary --plugin=protoc-gen-grpc=ThirdParty\grpc_build\bin\grpc_cpp_plugin.exe

    命令执行成功后，GrpcLibrary目录下会生成HelloWorld.grpc.pb.cc、HelloWorld.grpc.pb.h、HelloWorld.pb.cc和HelloWorld.pb.h

    

    将其都添加到项目GrpcLibrary中。最后GrpcClient、GrpcServer分别引用类库GrpcLibrary。

3.服务端

// greeter_server.cc
#include 
#include 
#include 

#include 

#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 GrpcLibrary::HelloRequest;
using GrpcLibrary::HelloReply;
using GrpcLibrary::GrpcService;

// Logic and data behind the server's behavior.
class GreeterServiceImpl final : public GrpcService::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() {
    std::string server_address("0.0.0.0:50051");
    GreeterServiceImpl service;

    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(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) {
    RunServer();

    return 0;
}

4.客户端

// greeter_client.cc
#include 
#include 
#include 

#include 

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

using grpc::Channel;
using grpc::ClientContext;
using grpc::Status;
using GrpcLibrary::HelloRequest;
using GrpcLibrary::HelloReply;
using GrpcLibrary::GrpcService;

class GreeterClient {
public:
    GreeterClient(std::shared_ptr channel)
        : stub_(GrpcService::NewStub(channel)) {}


    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 stub_;
};

int main(int argc, char** argv) {

    GreeterClient greeter(grpc::CreateChannel(
        "localhost:50051", grpc::InsecureChannelCredentials()));
    std::string user("world");
    std::string reply = greeter.SayHello(user);
    std::cout << "Greeter received: " << reply << std::endl;

    return 0;
}

5.测试

   先启动服务的，再启动客户端。