Can anyone help with my problem?

Dear all,

I've successfully compiled ccrtp on my windows platform.
Originally on Windows 2000 sp4 and later Windows XP with VS .NET 2003.
The sample program rtplisten and rtpsend work just fine for me on
Windows 2000 sp4.
But when I follow the same step on Windows XP.
No network packet was sent out.
Rtpsend mentioned that it has sent out the packet.
But rtplisten wouldn't get the packet.:(
But the rtphello works just fine.

Thank you for your time and look forward to your reply.

Sincerely,
Kun