The additional boolean webSocketUrl capability is used to request a WebDriver BiDi websocket: https://w3c.github.io/webdriver-bidi/#establishing

Similar to the moz:debuggerAddress capability it needs to be validated by Marionette, and has make sure to create to return the Websocket URL. When webSocketUrl is set it should be asserted for true.

Returned will be a WebSocket URI:
https://w3c.github.io/webdriver-bidi/#construct-a-websocket-url

James, what actually defines the secure bit of the WebSocket connection? I assume that we should basically use it by default and only fallback if a secure connection cannot be established? I don't see how a client could actually request that.

Actually Marionette has to handle all that. Geckodriver just passes-through the URL.

James, mind having a look at my question from comment 0? Thanks.

https://w3c.github.io/webdriver-bidi/#start-listening-for-a-websocket-connection is called from the WebDriver New Session Algorithm in https://w3c.github.io/webdriver-bidi/#establishing Basically it's up to you whether the connection is ws:// or wss:// and the client has to deal with either.

(In reply to James Graham [:jgraham] from comment #2)

Basically it's up to you whether the connection is ws:// or wss:// and the client has to deal with either.

It would be good to know the overhead for secure websockets, but given that HTTPS is that highly promoted (versus HTTP) we should maybe also default to a secure websocket, which wouldn't allow sniffing on the network. If clients cannot handle that we might want to add another capability or preference to fallback to a non-secure websocket.

Depends on D119552

https://hg.mozilla.org/mozilla-central/rev/fd61434c223f