Golang socket io unable to establish websocket connection

user_16333822 0
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this is my socket io Go server, basically following the package's example code:

func main() {
    server := socketio.NewServer(nil)
    server.OnConnect("/", func(s socketio.Conn) error {
        s.SetContext("")
        fmt.Println("connected:", s.ID())       
        return nil
    })

    server.OnEvent("/", "notice", func(s socketio.Conn, msg string) {
        fmt.Println("notice:", msg)
        s.Emit("reply", "have "+msg)
    })

    server.OnEvent("/chat", "msg", func(s socketio.Conn, msg string) string {
        s.SetContext(msg)
        return "recv " + msg
    })

    server.OnEvent("/", "bye", func(s socketio.Conn) string {
        last := s.Context().(string)
        s.Emit("bye", last)
        s.Close()
        return last
    })

    server.OnError("/", func(s socketio.Conn, e error) {
        fmt.Println("meet error:", e)
    })

    server.OnDisconnect("/", func(s socketio.Conn, reason string) {
        fmt.Println("closed", reason)
    })

    go server.Serve()
    defer server.Close()

    mux := http.NewServeMux()
    
    mux.Handle("/socket.io/", server) // socket io
    
    log.Println("Serving at localhost:8000...")
    log.Fatal(http.ListenAndServe(":8000", cors.Default().Handler(mux)))
}

And this is my client side code:

<script src="https://cdn.socket.io/4.5.0/socket.io.min.js"
  integrity="sha384-7EyYLQZgWBi67fBtVxw60/OWl1kjsfrPFcaU0pp0nAh+i8FD068QogUvg85Ewy1k" crossorigin="anonymous"></script>
<script>
  const socket = io("http://localhost:8000");
  socket.emit("msg", "abc")
</script>

My client side just keep sending long-polling GET requests, the websocket connection cannot be established. I suspect it might have something to do with my server response? From the browser devtool, it seems like I have some random bytes in front of my response payload:

enter image description here

I wasn't able to solve the issue. Any help would be appreciated, thank you!

socket.io go websocket
1 Answers

You are using version 4.5.0 of the client along with (I assume - minimal reproducable examples please) github.com/googollee/go-socket.io. The go package readme states:

Current this library supports 1.4 version of the Socket.IO client. It supports room, namespaces and broadcast at now.

The socket io docs provide a compatibility chart showing that v1 of the server is only supported by version 1 of the client. So the following appears to work (playground - note I also made subtle changes so the message is output):

<script src="https://cdn.socket.io/socket.io-1.7.4.min.js"></script>
<script>
  const socket = io("http://localhost:8000");
  socket.emit("msg", "abc");
</script>

To use a later version of Socket.IO you will need a server that supports a later version of the protocol. gosf appears to support v2 but I have not tried it.

user_118109460
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