接上节说的grpc
关于protobuf需要安装protoc并get几个go包

go get -u github.com/golang/protobuf/proto
go get -u github.com/golang/protobuf/protoc-gen-go
go get google.golang.org/grpc

我们用grpc-go的例子来跑一跑
proto文件：

syntax = "proto3";

option objc_class_prefix = "HLW";

package helloworld;

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

生成pb文件

protoc --go_out=plugins=grpc:. helloworld.proto

里面包含了接口的定义
我们来看下服务端的代码

package main

import (
    "log"
    "net"

    pb "helloworld"
    "golang.org/x/net/context"
    "google.golang.org/grpc"
)

const (
    port = ":50051"
)

// server is used to implement helloworld.GreeterServer.
type server struct{}

// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
    return &pb.HelloReply{Message: "Hello " + in.Name}, nil
}

func main() {
    lis, err := net.Listen("tcp", port)
    if err != nil {
        log.Fatalf("failed to listen: %v", err)
    }
    s := grpc.NewServer()
    pb.RegisterGreeterServer(s, &server{})
    s.Serve(lis)
}

因为我直接把pb文件放在了GOPATH下面，所以pb这里直接指了helloworld
server端是起了一个grpc server，起在了50051端口上，类似于httpserver，grpc是基于http2的

看下客户端代码

package main

import (
    "log"
    "os"

    pb "helloworld"
    "golang.org/x/net/context"
    "google.golang.org/grpc"
)

const (
    address     = "localhost:50051"
    defaultName = "world"
)

func main() {
    // Set up a connection to the server.
    conn, err := grpc.Dial(address, grpc.WithInsecure())
    if err != nil {
        log.Fatalf("did not connect: %v", err)
    }
    defer conn.Close()
    c := pb.NewGreeterClient(conn)

    // Contact the server and print out its response.
    name := defaultName
    if len(os.Args) > 1 {
        name = os.Args[1]
    }
    r, err := c.SayHello(context.Background(), &pb.HelloRequest{Name: name})
    if err != nil {
        log.Fatalf("could not greet: %v", err)
    }
    log.Printf("Greeting: %s", r.Message)
}

用grpc.dial的方法建立了一个连接，然后建了一个client，通过client去和server通信，完成后再将conn断开。

先运行服务器，在运行客户端，可以看到。

2018/01/18 13:35:42 Greeting: Hello world