It's described in the manual. But it should work like this:

-copy anet.dll and anet.h (Lite-C) into your work folder
-set the plugindir to "." (you need to write this into a .wdl file that is named like your main source file)
-write #include "anet.h" into your main source file



Sounds like enet_clsend_event/enet_svsend_event. It let's a client/server call a function with a given parameter (msg).

I will look into the threads later (don't have time yet).