CORS error

[anshuljain633]

Hi @miguelgrinberg
I'm getting this error at the client:

Access to XMLHttpRequest at 'http://x.com/socket.io/?EIO=4&transport=polling&t=NVyXb_5' from origin 'http://x.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

polling-xhr.js:202 GET http://x.com/socket.io/?EIO=4&transport=polling&t=NVyXb_5 net::ERR_FAILED

i'm using supervisor to run gunicorn server

[program:gunicorn]
command=gunicorn --bind 0.0.0.0:5000 -k flask_sockets.worker app:app

client side code

<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/3.1.1/socket.io.js"></script>

    <script type="text/javascript">
            $(document).ready(function(){

                    // sending a connect request to the server.
                    var socket = io.connect('https://x.com');

                    // An event handler for a change of value
                    $('input.sync').on('input', function(event) {
            socket.emit('Slider value changed', {who: $(this).attr('id'), data: $(this).val()});
            return false;
        });

        socket.on('after connect', function(msg){
            console.log('After connect', msg);
        });

        socket.on('update value', function(msg) {
            console.log('Slider value updated');
            $('#'+msg.who).val(msg.data);
        });
            });
    </script>

server side ->

from flask import Flask, render_template
from flask_socketio import SocketIO, emit
from flask.ext.cors import CORS

app = Flask(name)
socketio = SocketIO(app,cors_allowed_origins="*")

values = {
'slider1': 25,
'slider2': 0,
}

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

@socketio.on('connect')
def test_connect():
emit('after connect', {'data':'Lets dance'})

@socketio.on('Slider value changed')
def value_changed(message):
values[message['who']] = message['data']
emit('update value', message, broadcast=True)

cors = CORS(app,resources={r"/":{"origins":""}})
if name == 'main':
socketio.run(app, host='0.0.0.0')

[miguelgrinberg]

The server configuration seems okay to me. Some intermediary that you have between your server and your client might be stripping the CORS headers from the responses.

[anshuljain633]

I'm using nginx container and supervisor to run gunicorn server.
everything works fine if i run application without application server(gunicorn or uwsgi) but when i configure any of application server i get this CORS error.
beside that i'm also using AWS ELB.
@miguelgrinberg

[selmanbaskaya]

@anshuljain633 Hi mate.

I am getting exactly the same error as you.
Did you solve this problem?