Player sets up server UNet.

I've been playing Unturned a lot lately and I want to know how to have a multiplayer system like that with UNet. In the menu you can click view servers and a bunch of servers hosted by people all over the world come up. Dedicated servers rented by youtubers or just a server hosted on a players computer. How to have something like this where the player sets up the server with UNet. None of that relay server or matchmaker.