The demodulator and decoder program described below makes use of the GNURadio framework.
The most basic part of the software is the P25 receiver program. This takes a signal source as its input and produces audio and a stream of messages as its output. The message streams can be captured to file or forwarded either to the TAP device or to a file for later processing. Instructions for getting and building the source code are available here.
A modified version of the WireShark packet sniffer is used to inspect the contents of the message stream. Custom dissectors pick apart the P25 messages and allow the inspection of individual data items. To use WireShark the source code distribution must be patched and then built and installed on the target platform. Details of this procedure can be found here.