Dire Wolf is a software "soundcard" modem/TNC and APRS * encoder/decoder. It can be used stand-alone to receive APRS messages, as a digipeater, APRStt gateway, or Internet Gateway (IGate). It can also be used as a virtual TNC for other applications such as APRSIS32, UI-View32, Xastir, APRS-TW, YAAC, UISS, Linux AX25, SARTrack, and many others. You'll need to edit the config file before first run to specify soundcard, etc.