defnet is directly based on Lua Sockets so it’s kinda just an implementation of that.
As this is still quite a new engine there are unfortunately not many open multiplayer examples out there, still the engine can absolutely do some great multiplayer games. We created a multiplayer game, https://blastlands.com/ from solely lua sockets and our own network lib.
If you have managed to do this on Unity (I guess HLAPI) and Godot I’m sure you will be able to understand defnet and give it a spin. I recommend it before trying out the Lua Sockets alone.
But first I would check out Colyseus and especially this forum thread: Colyseus - Tic Tac Toe Multiplayer Example