flask socketio CORS

Question

I've been trying to send data from flask over socket io. I need to access this data from a different origin, but it is giving a CORS error. I have tried using all kinds of cross origin stuff and none of it has worked. Can somebody help with this.

The view that should be called thought socket io:

from flask.ext.cors import cross_origin
@socketio.on('increment',namespace="/api")
@cross_origin()
def increment(message):
    number += 1;
    emit('number',{'data':number},broadcast=True)

Running the server:

app = Flask(__name__)
cors = CORS(app,resources={r"/api/*":{"origins":"*"}})
socketio = SocketIO(app)
app.debug = True
app.host = '0.0.0.0'

socketio.run(app)

Answer 1

I solved by following:

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

Answer 2

I had a similar issue, got it working with this setup:

#you may not need all these options
from flask import Flask, render_template, request
from flask.ext.socketio import SocketIO, emit, join_room, leave_room
from flask.ext.cors import CORS

app = Flask(__name__, template_folder='./', static_folder='./', static_url_path='')
app.config['SECRET_KEY'] = 'some-super-secret-key'
app.config['DEFAULT_PARSERS'] = [
    'flask.ext.api.parsers.JSONParser',
    'flask.ext.api.parsers.URLEncodedParser',
    'flask.ext.api.parsers.FormParser',
    'flask.ext.api.parsers.MultiPartParser'
]
cors = CORS(app,resources={r"/*":{"origins":"*"}})
socketio = SocketIO(app)
socketio.run(app,port=5000,host='0.0.0.0')

You can set up routes as such:

@app.route("/")
def indexRoute():
    return render_template('index.html',version=VER)

And socket requests:

@socketio.on('connect',namespace="/home")
def test_connect():
    print "client connected:",rooms()[0]

On the client side in JS i did the following:

var socket = io.connect('http://' + location.hostname + ':5000/home');
socket.on('connect',function(data) {
    console.log('connected to socket');
});

Also, take a look at this snippet from Flask developers.

Answer 3

For some reason, cors_allowed_origins="*" did not work for me. I had to instead specify the full address of the origin as the following:

socketio = SocketIO(app, cors_allowed_origins=['http://127.0.0.1:5500']) 

The error message that says "<client_address> is not an accepted origin. (further occurrences of this error will be logged with level info)" should indicate which address you should be typing in.

Answer 4

Check that you are using the supported version of socket.io in your html file.

<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/3.0.4/socket.io.js" integrity="sha512-aMGMvNYu8Ue4G+fHa359jcPb1u+ytAF+P2SCb+PxrjCdO3n3ZTxJ30zuH39rimUggmTwmh2u7wvQsDTHESnmfQ==" crossorigin="anonymous"></script>