Head over to the multiplayer forum
There's a FAQ there you should read.
In general (since I have no idea what language, API's or tools you will be using) there will be 1 client, that's the one the user is on. he will initially connect to the login machine which houses the lobby, etc. Then, when he plays the game, the login machine will direct the client to connect to the game server.
But, you've got a long way to go before you get to that point if this is your 1st time writing network code.
Thanks, But I was wondering about those 3 different aps I mentioned..
So when I go to login screen/launcher... and should that app shut down and then the lobby launches?
And when you start a game from the lobby, The lobby runs in the background?
Should game be child to lobby?
And is lobby father to launcher or child to launcher?
Just make it one application with multiple states instead, if you have a launcher its best to keep it simple and only use it to update the actual game (it shouldn't deal with things like logging in etc, just have it check that the game is up to date and then start the game)