How to start HoloPlay.js/Three.js mode?

#1

I followed the instructions in the doc, with no luck. The page tells me

Three.js driver not detected! Click OK to download. If you have already installed the driver, please make sure port 11222 is open.

but after installing the driver it still says the same thing.

I am able to launch the Library, that works.

Seems like something needs to be running on port 11222. What do I need to launch for that?