Server doesn't notice when client closes socket (.NET CF & GPRS)

Question

Client written in .NET Compact Framework. Client connects a socket to the server over a GPRS connection. The server accepts the connection. Client sends 62 bytes of data and then closes the socket. Server never detects that the client has closed the socket and is therefore not able to know that the transfer has completed.

This code works fine when run over a wireless connection.

Any ideas?