Cannot connect unity client with flask socket io

[esvelaren]

I'm running flask-socketio server (version 5.2.0) along with unity clients (running socketio version 3.x.x or 4.x.x ). The issue I'm having is whenever a client tries to connect to the server, I get HTTP 400 error message:

"GET /socket.io/?EIO=4&transport=websocket HTTP/1.1" 400 -

The server code looks as follows:

from gevent import monkey
monkey.patch_all()
    
from flask import Flask, render_template
    from flask_socketio import SocketIO, emit
    import uwb_logic_multiplayer
    from threading import Thread
        
    app = Flask(__name__)
    app.config['SECRET_KEY'] = 'secret!'
    socketio = SocketIO(app,async_mode='threading',cors_allowed_origins="*")
    uwb_thread = None
    
    @app.route('/start_uwb')
    def init():
        global uwb_thread
        if uwb_thread is None:
            # uwb_thread = socketio.start_background_task(uwb_logic_multiplayer.start_uwb, False, socketio)      
            print("----->Starting the node system")
            uwb_thread = Thread(target = uwb_logic_multiplayer.start_uwb, args=(False,socketio)) # args: verbose -> True or False
            uwb_thread.start()
        return "<h1>Starting UWB System...</h1>"
    
    @socketio.event
    def connect():
        print('----->Connected to a client!')
    
    @socketio.event
    def disconnect():
        print('----->Disconnected from a client!')
    
    if __name__ == '__main__':
        print("----->Starting the webserver")
        socketio.run(app, debug = True, host = "0.0.0.0", port=5000)
        print("----->End")

The client code (unity) looks as follows:

    namespace Altheria.TempNoname
    {
        public class SocketIoTest
        {
            private static SocketIoTest instance = null;
            public static SocketIoTest Instance
            {
                get
                {
                    if (instance == null)
                    {
                        instance = new SocketIoTest();
                    }
                    return instance;
                }
            }
            public void connect(Uri uri, Action<SocketIOResponse> onPositionChanged, Action<SocketIOResponse> onButtonPressed)
            {
                this.socket = new SocketIOUnity(uri, new SocketIOOptions
                {
                    Query = new Dictionary<string, string>
                    {}
                    ,
                    Transport = SocketIOClient.Transport.TransportProtocol.WebSocket
                });
                var jsonSerializer = new NewtonsoftJsonSerializer();
                socket.JsonSerializer = jsonSerializer;
                socket.OnConnected += async (sender, e) =>
                {
                    UnityEngine.Debug.Log("Connected to server");
                };
                this.socket.OnUnityThread("position_calibration", onPositionChanged);
                this.socket.OnUnityThread("light_button_pressed", onButtonPressed);
                socket.ConnectAsync();
                UnityEngine.Debug.Log(this.socket.Connected);
            }
            public SocketIOUnity socket { get; set; }
            public Task disconnect()
            {
                return this.socket.DisconnectAsync();
            }
        }
    }

    public class Test : MonoBehaviour
    {
        public TMP_Text text;
        // Start is called before the first frame update
        public SocketIoTest socket { get; set; }
        void Start()
        {
            this.text.SetText("Starting.");
            var uri = new Uri("http://192.168.1.40:5000");
            this.socket = SocketIoTest.Instance;
            socket.connect(uri, onPositionSyncronised, onPositionSyncronised);
            int x = 0;
            while (!socket.socket.Connected && x != 1000000) {
                x++;
                this.text.SetText("Not connected.");
            }
            if (!socket.socket.Connected) return;
            this.text.SetText("Online.");
        }
        void onPositionSyncronised(SocketIOResponse response)
        {
            //some code
        }
        void OnApplicationQuit()
        {
            this.socket.disconnect();
        }
    }
    public class Positioning
    {
        public double timestamp;
        public int   tag_number;
        public double x;
        public double y;
        public double uncertainity;
        public int anchors_used;
    }

I've also tried using different version of Flask, Flask-SocketIO, python-engineio, python-socketio and Werkzeug without success.

Appreciate any insights!

[miguelgrinberg]

Do you have logs from the server? Impossible to know what's going on without the logs.