Websocket endpoint and ProxyFixMiddleware

[hhakk]

I deployed a Quart app on Azure (using Docker), and they have some kind of reverse proxy that decrypts HTTPS traffic to HTTP traffic.

Now if I apply ProxyFixMiddleware and use url_for(<websocket-endpoint>) in my template, I correctly get a wss address rendered BUT Quart always responds with HTTP 400.

If I do not apply the middleware and manually set the protocol to wss on the template, I can succesfully establish a websocket connection. Why is this?

Using quart = 0.19.4 and hypercorn = 0.16.0

[Phil Jones]

Does the url_for result differ in the two circumstances? If so could you share the values