Golang 端口复用测试的实现

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。