pythongunicornpython-socketio

The WebSocket transport is not available, you must install a WebSocket server that is compatible with your async mode to enable it

When I development some socket.io service in python environment by using python-socketio and gunicorn, I meet an issue here.

I am using Mac OS X and I am using python 3.7.

Environment setting
$ pip install python-socketio
$ pip install gunicorn

server-side code
app.py

import socketio

sio = socketio.Server()
app = socketio.WSGIApp(sio, static_files = {
    '/': './socketio-client.html'
})

@sio.event
def connect(sid, environ):
    print(sid, 'connected')

@sio.event
def disconnect(sid):
    print(sid, 'disconnected')

client-side code
socketio-client.html

<html>
  <head>
    <title>Socket.IO Demo</title>
    <script src="https://cdn.socket.io/3.1.3/socket.io.min.js" integrity="sha384-cPwlPLvBTa3sKAgddT6krw0cJat7egBga3DJepJyrLl4Q9/5WLra3rrnMcyTyOnh" crossorigin="anonymous"></script>
  </head>
  <body>
    <h1>Socket.IO Demo</h1>
    <script>
      const sio = io();
      sio.on('connect', () => {
        console.log('connected');
      });

      sio.on('disconnect', () => {
        console.log('disconnected');
      });
    </script>
  </body>
</html>

Start program
I put the files in the same folder. And start it by following the command.
$ gunicorn --thread 50 app:app
enter image description here

I use the browser to open http://localhost:8000 and that works. Issue But there is an issue with the server

The WebSocket transport is not available, you must install a WebSocket server that is compatible with your async mode to enable it. See the documentation for details. (further occurrences of this error will be logged with level INFO)

I try to do
$ gunicorn --log-level INFO --thread 50 app:app
But I still cannot get helpful information from INFO log-level.

The code can keep going to run but the message shows me to install WebSocket server and I don't know which kind of package I need to install for this case of python-socketio or gunicorn.

What kind of package I missed to install? It's my first time to use python-socketio and gunicorn.
What should I do next?

Thanks for your help.

Solution

  • It just needs to install more packages here.
    $ pip install gevent-websocket
    $ pip install eventlet

    And then
    $ gunicorn --thread 50 app:app

    enter image description here

    Update 1:

    If the server-side need to active emit to client side, it will need this environment. Because this command $ gunicorn --thread 50 app:app cannot support this situation.

    The worked environment should be set by following.

    $ pip install eventlet==0.30.2
    $ gunicorn -k eventlet -w 1 app:app