From charlesreid1

Xastir is software for transmitting/receiving on the APRS network using AX25.

Xastir can interface with hardware like a TNC radio modem. Think of it as the software side of the TNC. If you set up an AX.25 kernel networking port, you can even have Xastir and another program (e.g., aprx daemon) using the TNC at the same time.

The main page of the project:

The manual: