Java multi-player game

Hi, I'd like to build a simple(ish) java multiplayer, I'd need a client/server, and also a java applet to build maps (and import into the game). The game is you can have a team of four soldiers, and the object is to type to team mates to plan how to attack the enemy positions, or hold and defend any captured flags (which are randomly placed on the map, each flag having different victory points) and the team at the end of the 15 minute time limit (or until all the enemy's soldiers are dead) with the most victory points win. You gain the victory points by tagging the flags and/or killing the enemy. The four soldiers can 'snipe', ie, take cover behind a wall etc and fire at the enemy, the closer the enemy or a stressed enemy from heavy fire running around in the open, the more chance of 'sniping' them. They can also grenade, (each soldier can be moved and perform these actions independently), if they hit an enemy with the grenade there's a random chance it will either kill the enemy, or simply stun the enemy. The enemy soldier will be stunned for 15 seconds if unstressed (ie: no bullets are whizzing past his ears), or 30 seconds if stressed. If grenaded again, the stun count will start again, and of course there's a random chance it might kill them. The graphics don't have to be anything fancy, I'm not after top of the range 3D graphics here, it's mostly about the strategy, gameplay and team work, that way it won't have any problems playing on older/slower machines. Of course controlling four soldiers in your unit you'll need to be able to zoom out, and have an aeirial/angled view.