socketio-client won't connect to wss flask-socketio server

I get the following error when trying to connect to a SSL encrypted Flask-socketio server using the websocket transport.

Attempting WebSocket connection to wss://localhost/socket.io/?transport=websocket&EIO=3
Traceback (most recent call last):
  File "client.py", line 6, in <module>
    sio.connect('https://localhost', transports=['websocket'])
  File "/Library/Python/3.7/site-packages/socketio/client.py", line 279, in connect
    six.raise_from(exceptions.ConnectionError(exc.args[0]), None)
  File "<string>", line 3, in raise_from
socketio.exceptions.ConnectionError: Connection error

Is there something more I need to configure for WSS to work? Unencrypted web sockets seem to work just fine.

Server.py

from flask import Flask
from flask_socketio import SocketIO

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

socketio.run(app, host='0.0.0.0', port=443, debug=True, keyfile='snakeoil.key', certfile='snakeoil.pem')

Client.py

import socketio

sio = socketio.Client(ssl_verify=False, logger=True, engineio_logger=True)
sio.connect('https://localhost', transports=['websocket'])
sio.disconnect()

Flask==1.1.1 Flask-SocketIO==4.3.0 python-engineio==3.12.1 python-socketio==4.5.1

[Professor-plum]

enabling engineio_logger shed enough light on the issue.

(84096) wsgi starting up on https://0.0.0.0:8080
(84096) accepted ('127.0.0.1', 65163)
http://localhost:8080 is not an accepted origin.
127.0.0.1 - - [08/May/2020 14:23:42] "GET /socket.io/?transport=websocket&EIO=3&t=1588969422.69502 HTTP/1.1" 400 122 0.000295

Adding cors_allowed_origins=[] to the server resolves the issue. This fix is a little dubious but acceptable

[miguelgrinberg]

Use cors_allowed_origins='http://localhost:8080' for increased security.