golang 实现tcp转发代理

package mainimport ("flag""fmt""io""net""os""strings""sync")var lock sync.Mutexvar trueList []stringvar ip stringvar list stringfunc 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)<-ExitChandconn.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}