I ran into the same issues trying to get the extension to work. A problem is also that the documentation is inconsistent.
Getting Started · isapir/lucee-websocket Wiki · GitHub and the related video suggest that you just need to install the extension via the Lucee Admin and you’re good to go. Though the README.md of the project claims that you additionally need to edit the web.xml. Websocket gateway :: Lucee Documentation, on the other hand, asks to create a WebSocket gateway after installing the extension, as mentioned by @Daemach.
And it looks like all three documentations are written by @isapir. Unfortunately, none of those three options work for me. So it would be fantastic to get some proper installation instructions.
(Sidenote: The Lucee Admin claims that version 1.1.3.1 is newer than 2.0.3, for some reason.)
Sebastian