How to create Lobby for Multiplayer

I want to start on a small multiplayer project.
My goal is to play with about 3 to 6 friends online. The idea is that if no servers exists in the lobby one player creates the server which then shows up in the lobby and the other ones can join.
Is this even possible to achieve with game maker? Where do I start?
For now I have followed this tutorial below and are comfortable with the basics but I dont know where to begin with a multiplayer game which you can play besides your own local network.