Elegant WebSockets for your Flask apps.

Heroku Python Team

Last update: Dec 26, 2022

Related tags

WebSocket flask-sockets

Overview

Flask-Sockets

Elegant WebSockets for your Flask apps.

Simple usage of route decorator:

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 request.cookies property.

Serving WebSockets in Python was really difficult. Now it's not.

Installation

To install Flask-Sockets, simply:

$ pip install Flask-Sockets

Deployment

A custom Gunicorn worker is included to make deployment as friendly as possible:

$ gunicorn -k flask_sockets.worker hello:app

Production services are provided by gevent and gevent-websocket.

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 app.run().

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.

WebSocket Interface

The websocket interface that is passed into your routes is provided by gevent-websocket. The basic methods are fairly straightforward — send, receive, send_frame, and close.

Release History

v0.2.1

Add support of Flask blueprints.

v0.2.0

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

v0.1.0

Initial release.

Comments

Use werkzeug URL routing (like Flask does) / get rid of middleware.
...ers.

This allows the use of parameters in URLs, for example a route of

@sockets.route("/chat/<name>/") def chat_channel(name): # ...

properly gets passed the channel name.
opened by mbr 13

The example code gives me an error?

I'm trying to use Flask-Sockets with the example code:

sockets = Sockets(app)

@sockets.route('/echo')
def echo_socket(ws):
    while True:
        message = ws.receive()
        ws.send(message)

Unfortunately it gives me an error saying:

    File "/Library/Python/2.7/site-packages/Flask-0.10-py2.7.egg/flask/app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
    File "/Library/Python/2.7/site-packages/flask_sockets.py", line 37, in __call__
    environment = environ['wsgi.websocket']
    KeyError: 'wsgi.websocket'

Anybody any ideas what I'm doing wrong? All tips are welcome!

opened by kramer65 12

Any kind of connection is tried to be upgraded to WS connection
Hello,

I am using both flask router and flash-sockets. That means, my server has both http and websocket end points. After flash-socket integration, any calls to my http router also try to upgrade the request. And getting following error.

Initializing WebSocket Sep 25 04:12:32 surcle app/web.1: Validating WebSocket request Sep 25 04:12:32 surcle app/web.1: Can only upgrade connection if using GET method.

This is how I register blueprint in init.py

from router import router, ws app.register_blueprint(router) sockets = Sockets(app) sockets.register_blueprint(ws)

And in router.py

router = Blueprint('router', __name__) ws = Blueprint('ws', __name__) @ws.route('/socket') def web_socket(socket): logging.debug('inside web_socket') while not socket.closed: message = socket.receive() socket.send(message) @router.route('/status', methods=['POST']) def status(): print "inside status"

What went wrong?
opened by winster 11
add werkzeug routing: allows '/endpoint/' style routing
This adds support for variable url paths just like with Flask's app.route decorator, so you can now do things like:

@sockets.route('/submit/<game_id>') def submit(ws, game_id): ...

I hadn't seen pull requests #7 and #14 before I wrote this, this is essentially the same thing but done differently (and with less changes) so maybe you'll like this better? I used werkzeug since this is what Flask is using. This works fine for me although I only tested it in the context of my project. If you think this doesn't make sense I'm happy to take suggestions and improve it, seems like this is a feature a lot of people want.
opened by jolleon 9
AttributeError: 'WebSocket' object has no attribute 'socket'

my flask version is 0.10. When I type gunicorn -k flask_sockets.worker chat:app, there is an error: AttributeError: 'WebSocket' object has no attribute 'socket' why?

opened by no13bus 8
add support for cookies in the websocket

if cookies are used for session handling, please note that you have to persist your session manually.

something like self.app.save_session(session, make_response("")) after messages are received does the trick.

opened by robertaistleitner 5
Using sockets with route pattern
I've got the following code, and it will open and immediately close the websocket connection.

@sockets.route('/sockets/<channel>') def echo_socket(ws): while True: message = ws.receive() ws.send(message)

Not quite sure if this is a feature request or a bug, but I think that WS routes should be able to accept flask route patterns.
opened by issackelly 4
Send a message to a single client

How could I send a message to a single client that is connected? I'm looking for something to send a notification to a logged in user that something is ready or so. Ideas?

opened by wiesson 4
Documentation on sending binary data?

I'd like to send binary data using this library, but I have no idea how to get there. So far I'm only getting encoding errors - probably because it's assumed that I'm sending ASCII strings. How to get around that?

opened by d33tah 3
blueprint issue
In my router.py, when I tried to create sockets object, it failed with following error

AttributeError: 'Blueprint' object has no attribute 'wsgi_app'

This is how I tried to create sockets object.

router = Blueprint('router', __name__) sockets = Sockets(router)

Since above statements didnt work, I also tried to put the following code in __init.py__:

from router import router app.register_blueprint(router) sockets = Sockets(router) sockets.register_blueprint(router)

How to fix this?
opened by winster 3
Just added a small patch to make the flask_sockets.worker play nicely with gunicorn's access-logformat

Basically, this small patch makes flask_sockets.worker work with gunicorn's access log configuration (rather than the hard-coded .log_request() and .format_request() in pywsgi.WSGIHandler).

Happy to do some polishing :)

opened by tkrajca 3
Project Status?

I noticed that the last commit is from May 2017 and that the description includes [DEPRECATED]. @edmorley is this project still being maintained? If not, is there an up to date fork? Or should we just use WebSocket more directly as described here. Thank you!

opened by davidhariri 5
how to get a websockets address with gunicorn

when i run gunicorn -k flask_sockets.worker hello:app， I get a http address like http://0.0.0.0:3000, how I get a websockets address like ws://0.0.0.0:3000

opened by v-yunbin 0
TypeError: register() takes 3 positional arguments but 4 were given
When running the main I'm facing this TypeError.The source of the error is while registering the sockets in blueprint

app.register_blueprint(html, url_prefix=r'/') sockets.register_blueprint(ws, url_prefix=r'/')

app.register_blueprint seems to be working fine.
opened by AlbinDavid 3
Set websocket=True for Rule, fixes #81

This fixes the WebsocketMismatch which appears with Werkzeug 2.0.0.

The cause is a websocket request hits a rule which Werkzeug doesn't think is a websocket endpoint.

opened by tomviner 5

Incompatible with Werkzueg>=2.0

I'm experiencing werkzeug.routing.WebsocketMismatch: 400 Bad Request after the recent release of werkzueg and flask. I'm not really sure why this is, but the docs state:

you receive a WebsocketMismatch exception if the only match is a WebSocket rule but the bind is an HTTP request, or if the match is an HTTP rule but the bind is a WebSocket request.

Here's the traceback I'm observing:

Traceback (most recent call last):
  File "/venv/lib/python3.9/site-packages/gevent/pywsgi.py", line 999, in handle_one_response
    self.run_application()
  File "/venv/lib/python3.9/site-packages/geventwebsocket/handler.py", line 75, in run_application
    self.run_websocket()
  File "/venv/lib/python3.9/site-packages/geventwebsocket/handler.py", line 52, in run_websocket
    list(self.application(self.environ, lambda s, h, e=None: []))
  File "/venv/lib/python3.9/site-packages/flask/app.py", line 2464, in __call__
    return self.wsgi_app(environ, start_response)
  File "/venv/lib/python3.9/site-packages/flask_sockets.py", line 40, in __call__
    handler, values = adapter.match()
  File "/venv/lib/python3.9/site-packages/werkzeug/routing.py", line 2026, in match
    raise WebsocketMismatch()

opened by rmorshea 20

Incompatibility with Flask 2.0

Flask 2.0, which has been recently released, changes the prototype of Blueprint.register

This triggers an exception on this line: https://github.com/heroku-python/flask-sockets/blob/003660b70bbe16e218fb8b28377603e86e9d1b36/flask_sockets.py#L100

opened by mcejp 1