How to make a multiplayer game ?

Hi. I watched a multiplayer checkers game tutorial on Youtube and started making a multiplayer game.

Until now, two player gets connected. One of them is client, other is both client and host. They choose their heros. And they spawn near their towers. They can shoot the enemy or enemy tower.

So the problem is, I guess I shouldn’t instantiate a server because server will always be there and never be closed.

I mean now I’m opening two instance of game. But it should be three. I should open the server first. And when I open two instance of game, they should connect to server. How can I do that ? Will the server be in another project ?

Command Line Arguments and use -batchmode -nographics