I'd like to be able to send binary messages over websockets. In the absence of any real difference between byte arrays and strings in CC Lua, this would probably involve giving websockets a sendBinary method or making send take an optional second argument indicating binary mode.

I had to find this feature in the java source, where is good documentation for this?

On the wiki, where everything else is

Great, thanks @Lemmmy, I was looking for a wiki website and didn't consider Github's wiki.

There are also a Wiki Website for CC-Tweaked

That's the original computercraft though, correct? Which is outdated and mostly forelorn?

Nah, this one is the ComputerCraft one. Though the CC:T one is somewhat outdated in places (no binary flag there for instance!) - hence #133.