[aprssig] are write-only APRS-IS clients valid?
kd8gbh at woodsidelane.net
Mon Dec 2 13:30:56 CST 2013
On Mon, 2013-12-02 at 13:19 -0600, Pete Loveall AE5PL Lists wrote:
> From http://www.aprs-is.net/Connecting.aspx (it is not hidden) and has been discussed many times over the past decade on this SIG:
> "All core servers and most javAPRSSrvr servers (see the APRS Server page elsewhere on this site) support port 14580 as a user-defined filter port. This port begins by only sending message packets addressed to the client or addressed to stations gated to APRS-IS by the client. As with ALL bidirectional ports, ALL packets passed from the client are passed to APRS-IS on a verified connection (more on that later). Most javAPRSSrvr servers use javAPRSFilter to provide the server-side filtering capability. javAPRSFilter is an additive filter. In other words, you start by receiving almost nothing. When you add a filter, you now receive the original few packets plus the packets that meet your filter definition."
Some of the confusion may stem from the language here. "This port
begins by only sending message packets addressed to the client or
addressed to stations gated to APRS-IS by the client" would seem to
imply that if two or more igates sent the same packet to APRS-IS, they
should *both* receive messages destined for the stations originating
those packets. I'm not sure how to reduce duplicate transmissions in
that case, but the argument for sending messages back via *all* igates
is pretty compelling to me.
>From the discussion so far, I gather that this is not the case, and that
the server maintains some sort of most-recently-heard list. If it's
using that list to choose a single igate by which to route messages back
to stations, then I'd argue it isn't quite literally in keeping with the
description quoted above.
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