gofwd.go

package main

import (
    "io"
    "log"
    "net"
    "os"
)

func forward(conn net.Conn) {
    client, err := net.Dial("tcp", os.Args[2])
    if err != nil {
        log.Fatalf("Dial failed: %v", err)
    }
    log.Printf("Connected to localhost %v\n", conn)
    go func() {
        io.Copy(client, conn)
    }()
    go func() {
        io.Copy(conn, client)
    }()
}

func main() {
    if len(os.Args) != 3 {
        log.Fatalf("Usage %s listen:port forward:port\n", os.Args[0]);
        return
    }    

    listener, err := net.Listen("tcp", os.Args[1])
    if err != nil {
        log.Fatalf("Failed to setup listener: %v", err)
    }

    for {
        conn, err := listener.Accept()
        if err != nil {
            log.Fatalf("Failed to accept listener: %v", err)
        }
        log.Printf("Accepted connection %v\n", conn)
        go forward(conn)
    }
}