portforward

package main

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

func handle(source net.Conn) {
    defer source.Close();
    target, err := net.Dial("tcp", os.Args[2])
    if (err != nil) {
        fmt.Println(err)
        return
    }
    defer target.Close()

    c := make(chan int, 2)
    go func() {
        io.Copy(target, source)
        c <- 1
    }()
    go func() {
        io.Copy(source, target)
        c <- 2
    }()

    <-c
}

func main() {
    if len(os.Args) < 3 {
        fmt.Println(os.Args[0], "<listen port> <target addr>")
        return
    }
    ln, err := net.Listen("tcp", os.Args[1])
    if (err != nil) {
        fmt.Println(err);
        return;
    }
    for {
        conn, err := ln.Accept()
        if (err != nil) {
            fmt.Println(err)
            continue
        }
        go handle(conn)
    }
}