CODEWITHSUNDEEP
flasksocket.ioflask-socketio
LuLu
LuLu

Reputation: 11

socket.io client fails to connect to server

I'm trying to build a Flask server in Python that uses socket.io. As I have never used socket.io before I used the code from Miguel Grinberg to make a simple website to test if I can get it working. When I navigate to the website and then check the server-console I see requests coming in to "/socket.io/?EIO=4&transport=polling&t=<some code>" that are responded to with status code 200.

However, in my browser (Chrome) the console shows an error: "Uncaught DOMException: Failed to read the 'responseText' property from 'XMLHttpRequest': The value is only accessible if the object's 'responseType' is '' or 'text' (was 'arraybuffer')." screenshot

It seems to me like when calling io.connect in my javascript a request is made to the server but somehow the response or the processing of it fails which results in a failed connection.

Does anyone have any idea for why that happens and how to fix it?

My server side code is

from flask import Flask, render_template
from flask_socketio import SocketIO, emit

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret!'
socketio = SocketIO(app)

@app.route('/')
def index():
    return render_template('index.html')

@socketio.on('my event', namespace='/test')
def test_message(message):
    emit('my response', {'data': message['data']})

@socketio.on('connect', namespace='/test')
def test_connect():
    emit('my response', {'data': 'Connected'})

@socketio.on('disconnect', namespace='/test')
def test_disconnect():
    print('Client disconnected')

if __name__ == '__main__':
    socketio.run(app)

The Javascript running on the client side is

$(document).ready(function(){
  var socket = io.connect('http://' + document.domain + ':' + location.port + '/test');
  socket.on('my response', function(msg) {
      $('#log').append('<p>Received: ' + msg.data + '</p>');
  });
  $('form#emit').submit(function(event) {
      socket.emit('my event', {data: $('#emit_data').val()});
      return false;
  });
});

Upvotes: 1

Views: 902

Answers (1)

Doc Bobo
Doc Bobo

Reputation: 31

I recently ran into the same problem.

It seems that flask-socketio is compatible with Socket.IO 2.x but not with Socket.IO 3.0. In my case, downgrading the JS library on the client side solved the problem.

Upvotes: 2

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