Server used as client as well
 

Is it possible to setup a machine as a multiplayer server and then also use the same machine as a client for playing MOHAA? If so, how do I do it? Thanks.

Sure you can. I've never done it personally, but I believe it's done from within the game itself. Go into the multiplayer area of the War Room and click on start game. Set your options as you like and you should be able to play as well as host from the same machine.

Yes you can. What you do is start a dedicated server and then start the game, go to multiplayer and join your own game.
You can either start the server through the game and then start the game again and join your own server or create 2 shortcuts to Mohaa.exe and then add your commands to each shortcut, which is how I do it.
When you join you will find your game under 'Lan Games'.