tcp_reverse_proxy

package main

import (
	"flag"
	"fmt"
	"io"
	"net"
)

var (
	localAddr  = flag.String("l", ":7001", "local address")
	remoteAddr = flag.String("r", "localhost:80", "remote address")
)

func pipe(src, dst io.ReadWriter) {
	buff := make([]byte, 0xffff)
	for {
		n, err := src.Read(buff)
		if err != nil {
			fmt.Println(err)
			return
		}
		data := buff[:n]

		n, err = dst.Write(data)
		if err != nil {
			fmt.Println(err)
			return
		}
	}
}

func handle(localConn net.Conn) {
	rAddr, err := net.ResolveTCPAddr("tcp", *remoteAddr)
	if err != nil {
		panic(err)
	}

	remoteConn, err := net.DialTCP("tcp", nil, rAddr)
	if err != nil {
		panic(err)
	}

	defer localConn.Close()
	defer remoteConn.Close()

	//go io.Copy(localConn, remoteConn)
	//io.Copy(remoteConn, localConn)

	go pipe(localConn, remoteConn)
	pipe(remoteConn, localConn)

	fmt.Println("done!", localConn.RemoteAddr())
}

func main() {
	flag.Parse()

	lAddr, err := net.ResolveTCPAddr("tcp", *localAddr)
	if err != nil {
		panic(err)
	}

	listener, err := net.ListenTCP("tcp", lAddr)
	if err != nil {
		panic(err)
	}
	fmt.Println("listen", localAddr)
	for {

		localConn, err := listener.Accept()
		fmt.Println("accept", localConn.RemoteAddr())

		if err != nil {
			panic(err)
		}

		go handle(localConn)

	}

}