[Xastir] Xastir messaging question

[Joe Kirby]

Sorry if I am duping a question, but I have not been able to find any
answers in the archives.

I am using soundmodem with an old scanner to receive local APRS traffic.
I use my radio as a tracker. I have seen people send me messages, but I
don't seem able to reply. Is aprs2.net bi-directional? Is there some
other service which I should be using? Should I set the message to route
through the local digi?

Pointers are appreciated.