Multiplayer - different screen resolution

I'm creating a game similar to Pong, and I added multiplayer with Network Manager HUD. My problem is that when I start the game in two computers that have different screen resolution, game objects like walls, appear in different part of screen. I do not know how I can resolve it. I had thought to determinate the two resolutions and set the smallest resolution in both computers, but I do not know how to do, and I hope there is a better solution. How can I resolve ?