golang 实现tcp转发代理的方法

我就废话不多说了，直接上代码吧：

package main

import (
"flag"
"fmt"
"io"
"net"
"os"
"strings"
"sync"
)

var lock sync.Mutex
var trueList []string
var ip string
var list string

func main() {
flag.StringVar(&ip, "l", ":9897", "-l=0.0.0.0:9897 指定服务监听的端口")
flag.StringVar(&list, "d", "127.0.0.1:1789,127.0.0.1:1788", "-d=127.0.0.1:1789,127.0.0.1:1788 指定后端的IP和端口,多个用','隔开")
flag.Parse()
trueList = strings.Split(list, ",")
if len(trueList) <= 0 {
fmt.Println("后端IP和端口不能空,或者无效")
os.Exit(1)
}
server()
}

func server() {
lis, err := net.Listen("tcp", ip)
if err != nil {
fmt.Println(err)
return
}
defer lis.Close()
for {
conn, err := lis.Accept()
if err != nil {
fmt.Println("建立连接错误:％v\n", err)
continue
}
fmt.Println(conn.RemoteAddr(), conn.LocalAddr())
go handle(conn)
}
}

func handle(sconn net.Conn) {
defer sconn.Close()
ip, ok := getIP()
if !ok {
return
}
dconn, err := net.Dial("tcp", ip)
if err != nil {
fmt.Printf("连接％v失败:％v\n", ip, err)
return
}
ExitChan := make(chan bool, 1)
go func(sconn net.Conn, dconn net.Conn, Exit chan bool) {
_, err := io.Copy(dconn, sconn)
fmt.Printf("往％v发送数据失败:％v\n", ip, err)
ExitChan <- true
}(sconn, dconn, ExitChan)
go func(sconn net.Conn, dconn net.Conn, Exit chan bool) {
_, err := io.Copy(sconn, dconn)
fmt.Printf("从％v接收数据失败:％v\n", ip, err)
ExitChan <- true
}(sconn, dconn, ExitChan)
<-ExitChan
dconn.Close()
}

func getIP() (string, bool) {
lock.Lock()
defer lock.Unlock()

if len(trueList) < 1 {
return "", false
}
ip := trueList[0]
trueList = append(trueList[1:], ip)
return ip, true
}

来源：https://blog.csdn.net/fyxichen/article/details/51505542