Post success message back to the sender   

I am receiving a XML file from a service/port. 

Based on the contents of the xml file, I need to post back a success or 
failure message. I need to do that through my dotnet program. Can someone 
give me an example on how to post the message back to the sender?

date: Sat, 4 Feb 2006 23:56:10 -0800   author:   Jack