Error 400 when upgrading to websocket transport

[DaRealCodeWritten]

Describe the bug
Flask-SocketsIO + Flask, attempts to use websockets as transport results in a 400 response code and a traceback on the client side, using simple-websocket as the WS framework and NGINX as the reverse proxy
Nginx config is as follows

server {
    server_name czvr-bot.xyz;
    location / {
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_set_header X-Real-IP $remote_addr;
        proxy_pass http://czvr-bot.xyz;
    }

    # SSL (if wanted)
    listen 443 ssl;
    ssl_certificate fullchain1.pem;
    ssl_certificate_key privkey1.pem;
}

Expected behavior
Website upgrades to WSS for the connection between the site and the bot

Actual behavior
Client throws the below traceback and the website refuses the upgrade

Logs
Python-SocketIO client (A discord bot)

Traceback (most recent call last):
  File "C:\Users\Eric Lysne\PycharmProjects\VancouverSite\bot.py", line 318, in inner
    await sock.connect("https://czvr-bot.xyz", transports="websocket")
  File "C:\Users\Eric Lysne\PycharmProjects\VancouverSite\venv\lib\site-packages\socketio\asyncio_client.py", line 149, in connect
    raise exceptions.ConnectionError(exc.args[0]) from None
socketio.exceptions.ConnectionError: Connection error

Flask-SocketIO server (A flask app)

Invalid websocket upgrade
INFO:engineio.server:Invalid websocket upgrade
INFO:werkzeug:127.0.0.1 - - [08/Aug/2022 01:16:37] "GET /socket.io/?transport=websocket&EIO=4&t=1659946597.8447661 HTTP/1.0" 400 -

What i've tried so far
Changing the https:// in the sock.connect() call to wss://
Modifying the order of the proxy directives in NGINX
Adding HTTP version directive in NGINX

[miguelgrinberg]

I converted this to a discussion because at this time I don't really have an indication that there is a bug here.

The "Invalid websocket upgrade" error occurs when the client sends a malformed websocket connection request, such as for example, one that does not include the proper upgrade HTTP headers. My guess is that your nginx configuration is causing this, and not your client. I suggest you look at the example configuration in the Flask-SocketIO documentation and try that approach to see if it helps.

[DaRealCodeWritten]

True, I'll take nginx out of the equation for now and give 'er a try

[DaRealCodeWritten]

Update: Removed NGINX and connected direct to the webserver, it accepted the upgrade and is functioning as expected, im not sure what NGINX is doing to prevent the upgrade

[DaRealCodeWritten]

Another update on the situation, i added

map $http_upgrade $connection_upgrade {
    default upgrade;
    '' close;
}

to NGINX and reattempted connecting through NGINX, and the webserver accepted the upgrade to WSS as expected

[miguelgrinberg]

Not sure why this makes a difference for you, as I have never needed to include this. But in any case, it works so maybe the why isn't that important. :)

[DaRealCodeWritten]

Might be because i removed the include proxy_params; since nginx whines about it if its included, which might be because im using nginx for windows