Preparing
> brew update && brew install protobuf
Create a go project(ex: lets-learn-golang-grpc)
> mkdir lets-learn-golang-grpc
> cd lets-learn-golang-grpc
llgg > go mod init lets-learn-golang-grpc
llgg > go get -u google.golang.org/grpc
llgg > go get -u google.golang.org/protobuf/proto
llgg > go get -u google.golang.org/grpc/cmd/protoc-gen-go-grpc
The go modules will be used whole the project.
Create a `chapter-00` for `helloworld` such as,
├── chapter-00
│ └── helloworld
│ ├── README.md
│ ├── client
│ │ └── main.go
│ ├── pb
│ │ ├── helloworld.proto
│ └── server
│ └── main.go
├── go.mod
└── go.sum
Create `pb/helloworld.proto`
syntax = "proto3";
option go_package = "lets-learn-golang-grpc/chapter-00/helloworld/pb";
package pb;
// The service definition
service HelloWorld {
// Sends the SayHello message
rpc SayHello (HelloRequest) returns (HelloResponse) {}
}
// The request message containing a name(Client-side)
message HelloRequest {
string name = 1;
}
// The response message containing a message(Server-side)
message HelloResponse {
string message = 1;
}
The name
will receive from the client
(user) and send a message to the client
.
Generate go codes with `pb/helloworld.proto`
chapter-00/helloworld > protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=. --go-grpc_opt=paths=source_relative pb/helloworld.proto
This will create two go codes, helloworld.pb.go
and helloworld_grpc.pb.go
.
├── pb
├── helloworld.pb.go
├── helloworld.proto
└── helloworld_grpc.pb.go
Create a server `server/main.go`
package main
import (
"context"
"lets-learn-golang-grpc/chapter-00/helloworld/pb"
"log"
"net"
"google.golang.org/grpc"
)
const (
port = ":50051"
)
type server struct {
pb.UnimplementedHelloWorldServer
}
// SayHello implements a server
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloResponse, error) {
log.Printf("Received: %v", in.GetName())
return &pb.HelloResponse{Message: "Hello " + in.GetName()}, nil
}
func main() {
lis, err := net.Listen("tcp", port)
if err != nil {
log.Fatalf("failed to listen: %v", err)
}
s := grpc.NewServer()
pb.RegisterHelloWorldServer(s, &server{})
log.Printf("server listening at %v", lis.Addr())
if err := s.Serve(lis); err != nil {
log.Fatalf("failed to serve: %v", err)
}
}
This server will return a message “Hello ” and a name that user send.
Create a client `client/main.go
`
package main
import (
"context"
"lets-learn-golang-grpc/chapter-00/helloworld/pb"
"log"
"os"
"time"
"google.golang.org/grpc"
)
const (
address = "localhost:50051"
defaultName = "World"
)
func main() {
conn, err := grpc.Dial(address, grpc.WithInsecure(), grpc.WithBlock())
if err != nil {
log.Fatalf("did not connect: %v", err)
}
defer conn.Close()
c := pb.NewHelloWorldClient(conn)
// get a name otherwise defaultName
name := defaultName
if (len(os.Args)) > 1 {
name = os.Args[1]
}
ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
defer cancel()
r, err := c.SayHello(ctx, &pb.HelloRequest{Name: name})
if err != nil {
log.Fatalf("could not say: %v", err)
}
log.Printf("Say: %s", r.GetMessage())
}
This server will send a name to server and receive a message from the server. The default name is World
.
Directory tree
.
├── chapter-00
│ └── helloworld
│ ├── README.md
│ ├── client
│ │ └── main.go
│ ├── pb
│ │ ├── helloworld.pb.go
│ │ ├── helloworld.proto
│ │ └── helloworld_grpc.pb.go
│ └── server
│ └── main.go
├── go.mod
└── go.sum
Run the server in the root of project or the server directory
> go run ./chapter-00/server/main.go
Run the client in the root of project or the client directory
> go run ./chapter-00/client/main.go
The result is
> Say: Hello World
When you put a name such as
> go run ./chapter-00/server/main.go Alice
you will have
> Say: Hello Alice
This is a very simple golang-gRPC example.