network port forwarding in go lang

go_port_forwarding.go

package main

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

func main() {
	ln, err := net.Listen("tcp", ":8080")
	if err != nil {
		panic(err)
	}

	for {
		conn, err := ln.Accept()
		if err != nil {
			panic(err)
		}

		go handleRequest(conn)
	}
}

func handleRequest(conn net.Conn) {
	fmt.Println("new client")

	proxy, err := net.Dial("tcp", "127.0.0.1:80")
	if err != nil {
		panic(err)
	}

	fmt.Println("proxy connected")
	go copyIO(conn, proxy)
	go copyIO(proxy, conn)
}

func copyIO(src, dest net.Conn) {
	defer src.Close()
	defer dest.Close()
	io.Copy(src, dest)
}

This go app forwards datas from localhost:8080 to localhost:80

Hi @qhwa

Great concept.
I have a question, how to capture request and response header ?
I want to check that header and then split into several destinations.
For example:

• header contains "websocket" dial to localhost port 8880
• header contains "cloudflare" dial to localhost port 8000
• etc.

Hi @masbur

I think other than a simple port-forwarding, what you want is a reverse proxy. In that case, there are some resources, such as this and this on top of reverseproxy.go.