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Greetings.
You're not going to be happy with some of the things you're about to learn about APRS text messaging. For text messages relayed through APRS-IS, the sender doesn't know and can't specify the recipient's position on the APRS-IS anyway. All I-gates in range of the sender will forward the text message to the backbone; the backbone will de-duplicate those forwards. Any I-gates currently on the backbone who have heard and reported the recipient _beaconing_ within some time interval (don't know the exact interval) will be sent the text message on the assumption those are Tx-capable I-gates who can forward the message to the final recipient. Other I-gates won't receive the message (unless they are using filters to ask for additional traffic and the message matches the filters). The text message is transmitted once by those Tx-capable I-gates as soon as it is received and there is clear channel at the I-gate. If the sender sends it again, the suitable I-gates (according to updated received traffic history at the time of the resend) will forward it again. There is no place that messages are "held"; if the recipient isn't listening at the time the message is transmitted, they won't get it. Period. The reason that aprs.fi always has it is because aprs.fi is always connected 24/7/365 and therefore never misses any traffic that makes it to the APRS-IS backbone. WHO-IS (and ANSRVR and others) are APRS-IS clients that have no RF capability, so they can only be accessed by stations either directly connected to the APRS-IS, or in range of a Tx-capable I-gate. They are all robots with a specified response behavior for a type of message sent to them. Hope this explains. Sorry for the disappointing news. Andrew, KA2DDO author of YAAC (an APRS-IS client and I-gate, among other things) ________________________________________ From: [email protected] <[email protected]> on behalf of Bob Cameron via groups.io <bob3bob3@...> Sent: Saturday, January 18, 2025 5:00 PM To: [email protected] Subject: [direwolf] APRS messaging query Looking to understand some obscure things about APRS messaging. In Understanding-APRS-Packets.pdf on John's aprsspec github site. (Tnx John!) RF to RF on same channel, well understood. Also understood is that the delivery will be retried until timed out, an ack is received or send cancelled. RF to RF via an IGate says can be done, but how does one know the recipients current RF location? Is it just automatic when WIDE hops are used? Also could the recipients closest RF TX site be explicitly defined in the digi path? The WHOIS server example is a bit confusing, but in essence appears to be a robot data response. My main question though is how does one poll for a message "being held not deliverable" in IS? (Mainly I think in VK as Inet>RF messaging seems disabled) I use Xastir to only display/list the RF channel and usually leave the Internet Server interface down, but now wonder if up and the filter parameter t/m/VK* will work? (I have TX disabled on this interface too.) I know too there is a facility to send messages from the CLI, but is there a method to pull down "held" messages? Tnxs Bob VK2YQA |
