FGCOM realizes a realtime radio/voice-communication for simulation applications (especially for Flightgear but maybe also for other simulations/games). Because I am a lazy programer I try to use existing software to fit my requirements. So the voice transmission is build onto VoIP (realized with Asterisk). Radio frequencies are simulated by conference rooms. The glue between VoIP and Flightgear (the client) is written in C using the libiaxclient iaxclient-library. The communication between the client and the registrar server is based onto XML-RPC XML-RPC (realized with libxmlrpc).