Does anyone have experience with the performance hit that is taken by a PC using TCP in listening 'mode' vs. UDP. I understand that UDP is a connection-less protocol and because of that the system overhead should be almost nothing. I would perfer to use TCP because of the better access to the various 'STATES' that can be inquired on. Our application requires that each PC load a 'Server' program that logs it's IP address into a table. Then our 'Client' program can review all of the logged in PC's look up their IP addresses in the table and send shutdown messages and automatically shut down the Server PC. We have this working as a UDP application, but would like to go to TCP if the 'Listen' method does not degrade a PC's or the networks performance.