It isn't mandatory to use a standardized subprotocol, all that's required is that the client & server agree
https://developer.mozilla.org/en- US/docs/Web/HTTP/Protocol_upgrade_mechanism "The subprotocols may be selected from the IANA WebSocket Subprotocol Name Registry or may be a custom name jointly understood by the client and the server." QEMU used/required 'binary' because that is what noVNC used when the QEMU websockets code was first implemented. It appears that noVNC was changed though to not send a "binary" subprotocol in commit f8318361b1b62c4d76b091132d4a8ccfdd2957e4 Author: Pierre Ossman <oss...@cendio.se> Date: Sat Oct 14 12:45:56 2017 +0200 Remove wsProtocols setting It isn't in use anymore since we deprecated support for Base64 mode. >From QEMU's POV looks like we'll need to tweak code to treat 'binary' and no sub-protocol as being equivalent. -- 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: New 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