Elegant WebSockets for your Flask apps.
Simple usage of
from flask import Flask from flask_sockets import Sockets app = Flask(__name__) sockets = Sockets(app) @sockets.route('/echo') def echo_socket(ws): while not ws.closed: message = ws.receive() ws.send(message) @app.route('/') def hello(): return 'Hello World!' if __name__ == "__main__": from gevent import pywsgi from geventwebsocket.handler import WebSocketHandler server = pywsgi.WSGIServer(('', 5000), app, handler_class=WebSocketHandler) server.serve_forever()
Usage of Flask blueprints:
from flask import Flask, Blueprint from flask_sockets import Sockets html = Blueprint(r'html', __name__) ws = Blueprint(r'ws', __name__) @html.route('/') def hello(): return 'Hello World!' @ws.route('/echo') def echo_socket(socket): while not socket.closed: message = socket.receive() socket.send(message) app = Flask(__name__) sockets = Sockets(app) app.register_blueprint(html, url_prefix=r'/') sockets.register_blueprint(ws, url_prefix=r'/') if __name__ == "__main__": from gevent import pywsgi from geventwebsocket.handler import WebSocketHandler server = pywsgi.WSGIServer(('', 5000), app, handler_class=WebSocketHandler) server.serve_forever()
Combining WebSockets with Ajax (XHR) endpoints also comes handy with the support of session handling built-in to sockets as well. As an example you could use an Ajax login call which would create a new session and accordingly set a secure HttpOnly cookie to the browser. After authorization, you can connect to the WebSocket endpoint and reuse the session handling from Flask there as well (as shown here: https://pythonhosted.org/Flask-Session/). Access to other custom cookies is also possible via Flasks
Serving WebSockets in Python was really difficult. Now it’s not.
To install Flask-Sockets, simply:
$ pip install Flask-Sockets
A custom Gunicorn worker is included to make deployment as friendly as possible:
$ gunicorn -k flask_sockets.worker hello:app
The given example can run standalone as main.
Anything that inserts
wsgi.websocket into the WSGI environ is supported, but gevent-websocket is recommended.
Development / Testing
Because the Werkzeug development server cannot provide the WSGI environ with a websocket interface, it is not possible to run a Flask app using the standard
If you try to, Flask will still try to serve on all the specified routes, and throw a
KeyError whenever a client tries to connect to a websocket route.
Instead, just use the included gunicorn worker (explained above), or anything that can insert
wsgi.websocket into the WSGI environ.
The websocket interface that is passed into your routes is provided by gevent-websocket. The basic methods are fairly straightforward —
- Add support of Flask blueprints.
- Add request context into the socket handler.
- Fallback to Flask logic if websocket environment is not available.
- Use Flask routing to allow for variables in URL
- Initial release.