I'm trying to connect my backend (python, flask) and frontend (react) with sockets, but the every time the sockets are around 20 seconds late.

backend:

from flask_socketio import SocketIO, emit
from flask import Flask
from flask_cors import CORS

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret!'
socketio = SocketIO(app, cors_allowed_origins="*")
CORS(app)

socketio.emit('message', 'test')

if __name__ == '__main__':
    socketio.run(app, debug=True, host='0.0.0.0')

frontend:

const App = () => {

    const [message, setMessage] = useState("")

    useEffect(() => {
        const socket = io('http://localhost:5000')
        socket.on("message", data => {
            setMessage(data)
        })
    }, [])

    return (
        <div>
            {message}
        </div>
    )
}

So the word test appears 20 seconds after loading the page. Why? Is it possible to do it faster?