Golang 端口复用测试

先给出结论：

同一个进程，使用一个端口，然后连接关闭，大约需要30s后才可再次使用这个端口。

测试

首先使用端口9001连接服务端，发送数据，然后关闭连接，接着再次使用端口9001连接服务端，如果连接失败，间隔15s后，再次尝试，最多尝试3次，。

client

package main


import (

	"bufio"
	"fmt"
	"net"
	"os"
	"time"
)


func DialCustom(network, address string, timeout time.Duration, localIP []byte, localPort int)(net.Conn,error) {
	netAddr := &net.TCPAddr{Port:localPort}

	if len(localIP) != 0 {
		netAddr.IP = localIP
	}

	fmt.Println("netAddr:", netAddr)

	d := net.Dialer{Timeout: timeout, LocalAddr: netAddr}
	return d.Dial(network, address)
}


func getOneConn() {

	serverAddr := "127.0.0.1:8080"

	// 172.28.172.180
	//localIP := []byte{0xAC, 0x1C, 0xAC, 0xB4}  // IP
	localIP := []byte{} //  any IP
	localPort := 9001

	var conn net.Conn
	var err error

	for i:=0;i<3;i++{

		conn, err = DialCustom("tcp", serverAddr, time.Second*10, localIP,localPort)
		if err != nil {
			fmt.Println("dial failed:", err)
			if i == 2 {
				os.Exit(1)
			}
			time.Sleep(15*time.Second)
		} else {
			break
		}
	}

	defer conn.Close()


	buffer := make([]byte, 512)
	reader := bufio.NewReader(conn)

	n, err2 := reader.Read(buffer)
	if err2 != nil {
		fmt.Println("Read failed:", err2)
		return
	}

	fmt.Println("count:", n, "msg:", string(buffer))

}




func main() {

	getOneConn()
	fmt.Println("=========================")
	getOneConn()
	fmt.Println("=========================")
	select{}

}

server

package main

import (
	"fmt"
	"net"
	"log"
)

func main() {

	addr := "0.0.0.0:8080"

	tcpAddr, err := net.ResolveTCPAddr("tcp",addr)

	if err != nil {
		log.Fatalf("net.ResovleTCPAddr fail:%s", addr)
	}

	listener, err := net.ListenTCP("tcp", tcpAddr)
	if err != nil {
		log.Fatalf("listen %s fail: %s", addr, err)
	} else {
	
		log.Println("rpc listening", addr)
	}


	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Println("listener.Accept error:", err)
			continue
		}
	
		go handleConnection(conn)
	
	}

}


func handleConnection(conn net.Conn) {

	//defer conn.Close()

	var buffer []byte = []byte("You are welcome. I'm server.")

	n, err := conn.Write(buffer)

	if err != nil {
	
		fmt.Println("Write error:", err)
	}
	fmt.Println("send:", n)

	fmt.Println("connetion end")

}

output

client输出：

$ ./client 
netAddr: :9001
count: 28 msg: You are welcome. I'm server.
=========================
netAddr: :9001
dial failed: dial tcp :9001->127.0.0.1:8080: bind: address already in use


netAddr: :9001
dial failed: dial tcp :9001->127.0.0.1:8080: bind: address already in use

netAddr: :9001
count: 28 msg: You are welcome. I'm server.
=========================

经过3次重试，30s后，才可以重新使用同一个端口9001进行连接。也就是同一个进程的情况狂下，一个连接关闭后，端口大约30s后才可以被使用。