I wonder if you've ever configured Babble on a Plesk managed server that uses Phusion Passenger for Node.js?
I got this response from Plesk support on setting up Node.js application on a a specific port.
The Node.js application must not run with the port on a production server. When Node.js application is deployed via Plesk Onyx, the application server (Phusion Passenger or iisnode) works with the web server to proxy requests from a site visitor (on ports 80/443) to the application
So I setup Babble in IPBoard with no port. The chat kind of works. What you type shows up in chat, but you can't see anyone in the room.
I tried following your page below, but the chat stopped working all together.