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[aprssig] Port 14580 Filter Bug? Or Is It Intentional?

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Sun Jul 8 22:38:08 UTC 2012


This feature of the 14580 port allows IGates to run with no specified 
filter and still be informed of stations that may have been heard via 
RF, but are also beaconing directly via APRS-IS.  Such stations should 
not have their messages gated from -IS to RF per number 4 at 
http://www.aprs-is.net/IGateDetails.aspx

> Gate message packets and associated posits to RF if all of the 
> following are true:
>
>  1. the receiving station has been heard within range within a
>     predefined time period (range defined as digi hops, distance, or
>     both).
>  2. the sending station has not been heard via RF within a predefined
>     time period (packets gated from the Internet by other stations are
>     excluded from this test).
>  3. the sending station does not have TCPXX, NOGATE, or RFONLY in the
>     header.
>  4. the receiving station has not been heard via the Internet within a
>     predefined time period.
>     A station is said to be heard via the Internet if packets from the
>     station contain TCPIP* or TCPXX* in the header or if gated
>     (3rd-party) packets are seen on RF gated by the station and
>     containing TCPIP or TCPXX in the 3rd-party header (in other words,
>     the station is seen on RF as being an IGate).
>

Without this feature from the APRS-IS server, there is no reasonable way 
for an IGate to become aware of the dual-nature of other stations.

Your desire to show a map with only RF receptions is why APRSISCE/32 has 
the View / RF / All display filter.  It provides a way for the map to 
show ONLY those stations heard recently via RF and will not show any 
residual stations that may have been updated from the -IS.  (View / RF / 
Local restricts to just recently local stations and View / RF / Direct 
shows only those recently received with no hops used).

Lynn (D) - KJ4ERJ -Author of APRSISCE for Windows Mobile and Win32


On 7/8/2012 1:49 PM, Pete Loveall AE5PL Lists wrote:
> This is correct operation, not a bug.  Port 14580 is an IGATE port.  It maintains a last-heard list of stations you have gated to APRS-IS and will present those stations back to you if they are heard directly on APRS-IS or if there is a message routed to that station and associated posits.
>
> Remember, when you create a filter, you are saying "I want these things in addition to what is normally served up on this port".  Exception filters do not override the port's native functions.  An IGate port always passes to the client all message packets (and associated posits) addressed to that client or addressed to a station that has been recently gated to APRS-IS by the client.  It also passes to the client all packets from a station that was recently gated to APRS-IS by the client where those packets indicate they were directly injected into APRS-IS.  The reason for this last part is so an IGate can determine if as station heard on RF also has a direct APRS-IS connection and, therefore, the IGate does not need to gate to RF messages for that APRS-IS connected station.
>
> 73,
>
> Pete Loveall AE5PL
> pete at ae5pl dot net
>
>> -----Original Message-----
>> From: Stephen H. Smith
>> Sent: Sunday, July 08, 2012 11:58 AM
>>
>> The only common thread I can see is that stations I once heard on RF and
>> igated
>> *TO* the APRS-IS later come back *FROM* the IS if:   either their station is
>> beaconing on both RF and Internet, or if they beacon with an identical
>> callsign/SSID on VHF and enter the APRS-IS from another igate.    This
>> happens
>> sometimes hours after HF propagation has caused the station to fade out on
>> HF.
>>      It's not obvious this is happening when you just look at the map, but is
>> very obvious when you look at the station details and see "Q" constructs and
>> TCPIP components in the path.
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