Begin on the server. Write your game logic. Then build your game client and connect it to the server
Once you have planned out your game. You should start your work on the server and write your game logic. The server library is a self contained web socket server. The library contains a default webpage handler and an embedded key value database, however you can plugin your own custom webpage handler and database.
On the server you start with the io.sockit.gameserver package. You can read the server docs for more information about this package but here is a simple way to think about the main classes.
The server is where you start. The server contains games and users. Games contain locations which contain rooms and rooms contain players
User logins create sessions and sessions become players when they join a room and take a seat
The Client connects to the server and joins a room. Room consists of Players. A Player represents a client that is seated in the Room. You need to define your own Client Event Listener which will receive events from the server.