APAF is a set of modules for Python that make it easier to develop network applications (it's built on top of Twisted) that run inside of darknets primarily (the Tor network, in particular). Cross platform. Designed to be run portably (i.e., without installation). Tries to make it as easy as possible to set up the networking stuff so you can concentrate on the application stuff. Engineered so that the traffic runs over Tor nicely and safely, but ensuring that you don't screw up and leak data is up to you.