I've made a simple Websockets server in Python using Flask + gevent-websocket.
The idea was taken from https://devcenter.heroku.com/articles/python-websockets
It uses Redis Pub/Sub subsystem to ensure that all connected clients receive the messages, even if there are several Gunicorn workers.
See the code here: https://github.com/warvariuc/flask-websockets
Feel free to comment and improve.