Websocket to TCP bridge

[Joseph Naegele]

Hi folks, I'm trying to implement a basic version of websockify using Gorilla websocket, however calling conn.NextReader() the first time appears to block forever.

My current attempt looks like this (with error handling removed):

upgrader := websocket.Upgrader{
    ReadBufferSize:  4096,
    WriteBufferSize: 4096,
    Subprotocols:    []string{"binary"},
    CheckOrigin: func(r *http.Request) bool { return true },
}

handler := func(w http.ResponseWriter, r *http.Request) {
    wsconn, err := upgrader.Upgrade(w, r, nil)
    defer wsconn.Close()

    conn, err := net.Dial("tcp", ":5900")
    defer conn.Close()

    writer, err := wsconn.NextWriter(websocket.BinaryMessage)
    defer writer.Close()

    _, reader, err := wsconn.NextReader()

    go io.Copy(conn, reader)
    io.Copy(writer, conn)
}

mux := http.NewServeMux()
mux.HandleFunc("/websockify", handler)

Note that I *am* checking all errors in my code (there aren't any). I've also tried changing the order of calling NextReader/NextWriter and dialing my remote TCP connection, as well as calling NextReader in an entirely different goroutine.

The following works when using golang.org/x/net/websocket:

handleWss := func(wsconn *websocket.Conn) {
    conn, err := net.Dial("tcp", ":8080")
    if err != nil {
        wsconn.Close()
    } else {
        wsconn.PayloadType = websocket.BinaryFrame

        go io.Copy(conn, wsconn)
        io.Copy(wsconn, conn)
    }
}

bootHandshake := func(config *websocket.Config, r *http.Request) error {
    config.Protocol = []string{"binary"}
    r.Header.Set("Access-Control-Allow-Origin", "*")
    r.Header.Set("Access-Control-Allow-Methods", "GET, POST, PUT, PATCH, DELETE")
    return nil
}

handler := websocket.Server{Handshake: bootHandshake, Handler: handleWss}
mux := http.NewServeMux()
mux.Handle("/websockify", handler)

Is my problem obvious? Any clues?

Thanks,
Joe