HTTP/2 extended connect error message doesn't blame the server

[Mrgaton]

Description

System.Net.Http.HttpRequestException: Failed to establish web socket connection over HTTP/2 because extended CONNECT is not supported. Try to downgrade the request version to HTTP/1.1.

Reproduction Steps

Conect to a websocket with Extended Connect

Expected behavior

Work?

Actual behavior

Exception

Regression?

No response

Known Workarounds

No response

Configuration

   conection = new ClientWebSocket();

   conection.Options.SetRequestHeader("Stream-Type", ",mystream");
   conection.Options.HttpVersion = HttpVersion.Version30;

   await conection.ConnectAsync(new Uri(webSocketUri), Net.client, CancellationToken.None);

Other information

No response

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[MihaZupan]

What server are you connecting to? You'll see that exception if it doesn't support HTTP/2 extended connects.

As for HTTP/3, WebTransport is not supported by .NET yet, see #43641.

[Mrgaton]

Im conecting to a httplistener wich is running net 9, but i gess that the problem was that extended connect was not suported on net 9 not on my server exception should be a bit more clear.

[MihaZupan]

.NET 9 does support extended HTTP/2 connects.
If you want to use WebSockets over H2, you'll have to switch to Kestrel. HttpListener isn't going to support anything modern, see #63941.

[Mrgaton]

Okay but to clarify that the problem is onthe server would be great? i will see to migrate whole server

[MihaZupan]

Tweaking the exception message to blame the server seems fine.
We could also remove "Failed to establish web socket connection" from the error from HttpClient since we're just dealing with the extended connect at that layer. It's fine to include that at the WS layer.

[Mrgaton]

I'm trying Kestrel and I see a lot of latency increase just in localhost where httplistener gets around 1-3 ms Kestrel gets around 90-110 ms