I am using Flask-socket.io. It works, but it keeps connecting and disconnecting. so first time it is not getting notification cause connection keeps connecting and disconnecting.
This is frontend code.

  <script src="https://cdn.socket.io/4.7.5/socket.io.min.js" integrity="sha384-2huaZvOR9iDzHqslqwpR87isEmrfxqyWOF7hr7BY6KG0+hVKLoEXMPUJw3ynWuhO" crossorigin="anonymous"></script>
  <script>
    // initialize socket for notification
    const socket = io('/notification', {
       reconnectionDelay: 2000,
       reconnectionDelayMax: 4000,
       ping_timeout: 6000
    });
    ...

And this is backend code

    app = create_app()
    babel = Babel(app, locale_selector=get_locale)
    mail = Mail(app)
    socketio = SocketIO(app)
    socketio.init_app(app, cors_allowed_origins="*")

    @socketio.on('connect', namespace='/notification')
    def handle_connect():
        if current_user.is_authenticated:
            join_room(current_user.username)
            print('connected to', current_user.username)
    return True

    @socketio.on('disconnect', namespace='/notification')
    def handle_disconnect():
        if not current_user.is_authenticated:
            leave_room(current_user.username)
            print("disconnected")
    return True

Can anyone help me this? I am really appreciate. Thanks.