Connection problems using TCP/IP sockets under Vista

Hi group,

I've developed a server application that receives TCP/IP connections using a
TIdTCPServer from some devices located in the local network. These devices
are not PCs.

Under XP everything goes fine, but under Windows Vista this TCP/IP
connections become invalid after some hours, even though the socket does not
raise an exception, it just stops receiving information. Data is being sent
every 4 seconds through the socket.

Does anybody have an idea why this happens?

Thanks!