specifically, websockets are blocked by the "XHR" component on the popup panel, which also blocks XmlRPC and the Fetch API. as a rule, you could block all XHR requests everywhere with:

    * * xhr block

What I actually do is block everything but first-party requests, apart from CSS and images:

    * * * block
    * * cookie block
    * * css allow
    * * frame block
    * * image allow
    * 1st-party * allow
    * 1st-party css allow
    * 1st-party frame allow
    * 1st-party image allow

i actually allow xhr on third-party requests once i enabled third-party requests, which makes it possible to "enable" a bunch of site with two clicks (popup panel then click on "all").