WebSocket handshake should be case insensitive

[maben-mw]

While all supported browsers do appear to use Connection: Upgrade with capital U and Upgrade: websocket with all lower case "websocket", and so the case-sensitive matches to Upgrade and websocket in app.py:

matlab-proxy/matlab_proxy/app.py

Lines 374 to 378 in 45276dc

	if (
	reqH.get("connection") == "Upgrade"
	and reqH.get("upgrade") == "websocket"
	and req.method == "GET"
	):

will work fine in most cases, according to RFC6455 these values should be ASCII case-insensitive matches.

This does in fact lead to issues in practice when using matlab_proxy behind a reverse proxy where the reverse proxy may have rewritten Upgrade as upgrade (e.g. if you literally configured NGINX according to the instructions on https://nginx.org/en/docs/http/websocket.html). Of course the configuration can be changed such that the reverse proxy outputs Upgrade as well, but that should not be needed according to the RFC spec.

[prabhakk-mw]

@maben-mw
Thank you for the detailed report and explanation. We will include these suggestions in the next release.