I can confirm the test steps mentioned above. In an unchanged scenario a formerly failing-to-connect case got working when replacing the qemu (on Focal) in use with a patched one.
Adding an SRU Template for Focal to the bug description ... -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1849644 Title: QEMU VNC websocket proxy requires non-standard 'binary' subprotocol Status in QEMU: Fix Released Status in qemu package in Ubuntu: Fix Released Status in qemu source package in Focal: Confirmed Bug description: When running a machine using "-vnc" and the "websocket" option QEMU seems to require the subprotocol called 'binary'. This subprotocol does not exist in the WebSocket specification. In fact it has never existed in the spec, in one of the very early drafts of WebSockets it was briefly mentioned but it never made it to a final version. When the WebSocket server requires a non-standard subprotocol any WebSocket client that works correctly won't be able to connect. One example of such a client is noVNC, it tells the server that it doesn't want to use any subprotocol. QEMU's WebSocket proxy doesn't let noVNC connect. If noVNC is modified to ask for 'binary' it will work, this is, however, incorrect behavior. Looking at the code in "io/channel-websock.c" it seems it's quite hard-coded to binary: Look at line 58 and 433 here: https://git.qemu.org/?p=qemu.git;a=blob;f=io/channel-websock.c This code has to be made more dynamic, and shouldn't require binary. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1849644/+subscriptions
