While using HLAPI.
Can it be used over WAN without matchmaking?
If so, is there a player limit?
Which class/component should I look into?
Yeah it can be used without matchmaking. Matchmaking is just part of Unity’s relay server service. There is no hard player limit, this will depend on the power and internet speed of the server hosting each game. I guess you should start looking at the NetworkManager as well as the NetworkIdentity because they are the two HLAPI components you will run into the most. From there I would dive deeper into messages and NetworkClient to get a firmer grasp of what goes on behind the HLAPI.
That was my problem. At the end, I figured part of it deploying some tests, but anyway, thanks.
The relay server is something I couldn’t really figured out, but I think (for the most part) this shouldn’t be a problem for a direct connect to a server.