Upgrade to websocket transport on beta/ngs

[ezio-melotti]

socketio supports two types of transport: websockets and HTTP long-polling:

Even if most browsers now support WebSockets (more than 97%) [HTTP long-polling] is still a great feature as we still receive reports from users that cannot establish a WebSocket connection because they are behind some misconfigured proxy.

I noticed that when using `simoc-sam` locally, the transport is automatically upgraded to use websockets (click to see screenshot).


This however doesn't happen for the sim backend. I spent some time investigating and it seems likely that we have some misconfiguration in both nginx (used locally and on beta) and traefik (used on GCP).

The socketio docs have a section about sockets stuck in HTTP long-polling that link to another page with a recommended nginx configuration. However we already have something similar in

https://github.com/overthesun/simoc/blob/87dbc5c1085e37553fcc494ff04f41c02f9e75c9/nginx/proxy_ws_params#L1-L6

which is then imported in

https://github.com/overthesun/simoc/blob/87dbc5c1085e37553fcc494ff04f41c02f9e75c9/nginx/simoc_nginx.conf.jinja#L75-L79

even though it doesn't seem to work.

The traefik config files don't seem to mention websockets.

---

I also noticed that we are disabling CORS checks on the sim backend, so once we fixed these issues we should look into updating this with something stricter: https://github.com/overthesun/simoc/blob/87dbc5c1085e37553fcc494ff04f41c02f9e75c9/simoc_server/views.py#L34-L35

---

I also tried/investigated other things:

• Merged #255 in the sim backend (this repo), to ensure we are running the latest version
• After reading https://github.com/miguelgrinberg/Flask-SocketIO/discussions/1691:
  • I verified that the frontend (simoc-web) libraries are up to date
  • I verified that they work, since websockets work fine with the live backend (with no long-polling)
  • I checked vue-socket.io-extended but Vue3 support is still in alpha and the repo hasn't been updated in over a year.
  • vue-socket.io seems to support Vue2 too, with only basic Vue3 support from over a year ago. Both packages seems unnecessary.
• While connecting to the server, using http or ws doesn't seem to matter
• The proxy rules in vite.config.js are not the cause of the issue, since they should only apply to the local dev server, but might need to be tweaked while testing locally. The vite docs have an example about proxing websockets.

[ezio-melotti]

I fixed this in #446:

Without an additional websocket lib, our socketio connection relies on long polling. Starting from python-engineio 4.7.1, simple-websocket has been added, but it seems to have issues with gevent/gunicorn/flask. gevent-websocket seems to work fine.

We should still look into having stricter CORS checks.