How do I receive POST data in a C++ program

[Arjay]

The above does NOT require the presense of a separate web server application. (I think the WCF solution Arjay posted requires IIS, but I'm not sure, I'm not that into C#) If there's already a web server running, then there might be even simpler solutions by writing an extention/script for that instead.

WCF doesn't require IIS.

WCF can be hosted in multiple hosts:
IIS
Console app (.net)
Windows Form app (.net)
Windows Presentation app (.net)
Windows Service (.net)
Windows Activation Service