Can't establish WebTransport connection between Chrome and picoquicdemo

[tfrankowski]

I'm not able to establish a WebTransport connection between picoquicdemo server and Chrome browser. Specifically, I'm using this WebTransport client sample. Chrome is giving me Failed to establish a connection to https://xyz:4433/baton: net::ERR_METHOD_NOT_SUPPORTED. console message, which is not very helpful. "Event log" says Connection failed. WebTransportError: Opening handshake failed..
I can fetch the "Simple HTTP 3 Responder" website just fine from the server. I'm also able to successfully establish connection using pico_baton sample client.
I'm using Chrome 121 with "Experimental QUIC protocol", "WebTransport Developer Mode" and "Experimental Web Platform features" flags enabled.
Am I missing something? Should establishing such connection be possible? I'm happy to provide any details, that'd be helpful in troubleshooting the issue.

[huitema]

We need to understand whether the failure is at the web transport level, or whether it is an HTTP3 connection issue, or maybe a TLS issue. Do you have a capture (PCAP) of the exchanges between the Chrome browser and Picoquic?

[tfrankowski]

Seems like just fetching the sample website over HTTP3 works just fine. Here are captures for successful HTTP3 session and "failing" webtransport one. https://www.dropbox.com/scl/fo/qwvzzz4fn9eu1bdbgb7fp/h?rlkey=wakpzhqtjywntesedmhsjqwfd&dl=0