golang UDP, 绑定和非绑定地址到socket

UDP是无连接的，也就是说理论上不区分客户端和服务器。  服务器可以在一个端口上接收不同的客户端。

客户端可以先绑定服务器地址到socket上，也可以不绑定，发送和接收数据都指定服务器地址。

下面是测试代码：

package main

import (
	"encoding/json"
	"fmt"
	"net"
	"testing"
	"time"
)

const SvrAddr = "127.0.0.1:1111"
const CliAddr = "127.0.0.1:2222"

func ListenUDP(addrStr string) (*net.UDPAddr, *net.UDPConn, error) {
	addr, err := net.ResolveUDPAddr("udp", addrStr)
	if err != nil {
		fmt.Println("resolve udp addr failed:", err)
		return nil, nil, err
	}

	conn, err := net.ListenUDP("udp", addr)
	if err != nil {
		fmt.Println("listen udp svr failed:", err)
		return nil, nil, err
	}

	return addr, conn, nil
}

type Msg struct {
	Cmd string `json:"cmd"`
	Seq int    `json:"seq:`
}

func CliWriteTo(n int, cliConn *net.UDPConn, svrAddr *net.UDPAddr) {
	for i := 0; i < n; i++ {
		msg := Msg{
			Cmd: "echo",
			Seq: i,
		}
		data, err := json.Marshal(msg)
		if err != nil {
			fmt.Printf("send %d marshal failed:%v\n", i, err)
			break
		}
		//这里write, cliConn未绑定
		sendBytes, err := cliConn.WriteToUDP(data, svrAddr)
		if err != nil {
			fmt.Printf("send %d failed:%v\n", i, err)
			break
		}
		if sendBytes != len(data) {
			fmt.Printf("send failed, not equal send %v, but real %v\n", sendBytes, len(data))
		}
		var buf [128]byte
		recvBytes, _, err := cliConn.ReadFromUDP(buf[:])
		if err != nil {
			fmt.Printf("recv failed:%v\n", err)
			return
		}
		fmt.Println("CliRecv:", string(buf[:recvBytes]))
		time.Sleep(time.Second)
	}
}

func CliWrite(n int, cliConn *net.UDPConn, svrAddr *net.UDPAddr) {
	for i := 0; i < n; i++ {
		msg := Msg{
			Cmd: "echo",
			Seq: i,
		}
		data, err := json.Marshal(msg)
		if err != nil {
			fmt.Printf("send %d marshal failed:%v\n", i, err)
			break
		}
		//这里write, cliConn已经绑定
		sendBytes, err := cliConn.Write(data)
		if err != nil {
			fmt.Printf("send %d failed:%v\n", i, err)
			break
		}
		if sendBytes != len(data) {
			fmt.Printf("send failed, not equal send %v, but real %v\n", sendBytes, len(data))
		}
		var buf [128]byte
		recvBytes, _, err := cliConn.ReadFromUDP(buf[:])
		if err != nil {
			fmt.Printf("recv failed:%v\n", err)
			return
		}
		fmt.Println("CliRecv:", string(buf[:recvBytes]))
		time.Sleep(time.Second)
	}
}
func Server(svr *net.UDPConn) {
	ch := make(chan struct{}, 10)
	for {
		ch <- struct{}{}
		go func() {
			defer func() {
				<-ch
			}()
			var buf [128]byte
			recvBytes, cli, err := svr.ReadFromUDP(buf[:])
			if err != nil {
				fmt.Printf("recv failed:%v\n", err)
				return
			}
			//fmt.Println("SvrRecv:", string(buf[:recvBytes]))

			sendBytes, err := svr.WriteToUDP(buf[:recvBytes], cli)
			if err != nil {
				fmt.Printf("send back %d failed\n", err)
				return
			}
			if sendBytes != recvBytes {
				fmt.Printf("send back failed, not equal recv %v, send %v\n", sendBytes, recvBytes)
			}
		}()
	}
}

//UDP不区分客户端和服务器
//客户端和服务器可以同时Listen
//这个测试就是同时listen
func TestUDPSpeed(t *testing.T) {
	svrAddr, svrConn, err := ListenUDP(SvrAddr)
	if err != nil {
		t.Fatal(err)
	}
	cliAddr, cliConn, err := ListenUDP(CliAddr)
	if err != nil {
		t.Fatal(err)
	}
	fmt.Println(svrAddr, svrConn, cliAddr, cliConn)

	go Server(svrConn)

	CliWriteTo(10, cliConn, svrAddr)

}

//UDP dial,绑定远端端口
func TestUDPSpeedDial(t *testing.T) {
	svrAddr, svrConn, err := ListenUDP(SvrAddr)
	if err != nil {
		t.Fatal(err)
	}

	cliConn, err := net.DialUDP("udp", nil, svrAddr)
	if err != nil {
		t.Fatal(err)
	}
	fmt.Println(svrAddr, svrConn, nil, cliConn)

	go Server(svrConn)

	CliWrite(10, cliConn, svrAddr)

}

go test -v -run=Speed udp_test.go
go test -v -run=Dial udp_test.go