How do I print the data transmitted between local and remote? about tcp-proxy

[maxmcd]

Hey @faelp22

I've done it like this:

Create a writer that wraps the io.Writer for the connection

type closureWriter struct {
	fn     func([]byte)
	writer io.Writer
}

func newClosureWriter(fn func(p []byte), w io.Writer) io.Writer {
	return closureWriter{fn: fn, writer: w}
}

var _ io.Writer = new(closureWriter)

func (cw closureWriter) Write(p []byte) (len int, err error) {
	cw.fn(p)
	return cw.writer.Write(p)
}

Then you can set up the proxy like this:

func main() {
	flag.Parse()
	fmt.Printf("Listening: %v\nProxying: %v\n\n", *localAddr, *remoteAddr)

	listener, err := net.Listen("tcp", *localAddr)
	if err != nil {
		panic(err)
	}
	for {
		conn, err := listener.Accept()
		log.Println("New connection", conn.RemoteAddr())
		if err != nil {
			log.Println("error accepting connection", err)
			continue
		}
		go func() {
			defer conn.Close()
			conn2, err := net.Dial("tcp", *remoteAddr)
			if err != nil {
				log.Println("error dialing remote addr", err)
				return
			}
			defer conn2.Close()
			closer := make(chan struct{}, 2)
			go copy(closer, newClosureWriter(func(data []byte) {
				fmt.Printf("Data from %s to %s %q\n", conn.RemoteAddr(), *remoteAddr, data)
			}, conn2), conn)
			go copy(closer, newClosureWriter(func(data []byte) {
				fmt.Printf("Data from %s to %s %q\n", *remoteAddr, conn.RemoteAddr(), data)
			}, conn), conn2)
			<-closer
			log.Println("Connection complete", conn.RemoteAddr())
		}()
	}
}

Full working gist: https://gist.github.com/maxmcd/bb34f1dd466fc9e599cafc7252ee983a

[faelp22]

I did it that way but it didn't work

mensagem, _ := bufio.NewReader(conn).ReadString('\n')
fmt.Print("Mensagem recebida:", string(mensagem))

log.Println("New connection", conn.RemoteAddr())
if err != nil {
	log.Println("error accepting connection", err)
	continue
}
go func() {
	defer conn.Close()
	conn2, err := net.Dial("tcp", *remoteAddr)
	mensagem2, _ := bufio.NewReader(conn2).ReadString('\n')
	fmt.Print("Mensagem recebida2:", string(mensagem2))

[maxmcd]

going to close this issue, feel free to respond if you have other questions

[faelp22]

Thanks a lot for the help!