I believe you need to be more specific and give us a more accurate description on what you're trying to do.
Technically speaking, all streaming protocols I can think of are using "sockets". Meaning 2 ends are connected using a TCP or UDP port on which a "socket" file is transferred.

Regarding WSS, the principle is the same but using browsers directly (rather than software or hardware encoders streaming to a remote TCP server or decoder).
There's still a need for a "web server" usually secure (SSL) to provide both ends with the initial handshake and control the socket.

So, if your question is:
- can vMix act as a web server to provide WSS communication between remote browser clients, then the answer is no. It would require vMix to provide an URL for the remote end to connect to and have a mechanism to redirect the received data to its core.
But, if your question is :
- is it possible to "capture" what's happening in either ends of a WSS communication between browsers (handled by an external web server somewhere), then I think the answer is yes (on way or another)

> vMix has an integrated browser input. I'm not sure it will work because WSS is not supported by all browsers yet but it's worth a try. Just enter the url and see what happens.
> vMix can screencapture with audio what's happening in an external browser on your local network

Notes:
- I have already used vMix OUTPUT to feed a WSS client browser to push audio and video to a "server" via WSS.
- Technically speaking, it's very close from what vMixCall does but at the same time it's also very different. Not the same protocol !