Writing SW to monitor a host’s IP traffic

I am going to write a (simple) software that monitors all in- and outbound IP traffic on the same host that runs the application. When certain conditions are met (traffic to/from a certain application, with a specified host, on a specific port etc), the transferred data (or some of it) is to be logged to a plain file.

My question is quite low-level: Does anyone know how to “intrument” Windows to get notifications about all IP packets? I need code examples (preferably C++), or at least an idea of which API calls to use.

//Christer Sj?stedt