I am encountering an unusual issue. I have a send receive program for udp packets written in VB.net on a windows 2003 standard server. It receives from a custom piece of hardware and is supposed to send an acknowledgment. It sends the ack but it is not recognized on the other end. When the same program is run from my windows xp box the system works perfectly. The packet is still sent from the 2003 box but something is different. Any ideas at all on what could be the problem I posted in the windows 2003 forum and here?