Here you can view the Union API.
First-time developers will want to start with the Module and ModuleContext classes. Server modules add functionality server wide and room modules add functionality to you rooms.
Modules will be passed a ModuleContext by the server which is the starting point of interacting with the server. Use the ModuleContext to get a reference to the server which gives you access to rooms, clients and much more. Room modules can also get a direct reference to the room with which they are associated through the getRoom() method.