[aprssig] are write-only APRS-IS clients valid?

Dave Torrey 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.

Thanks,
Dave
KD8GBH



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