[OZAPRS] Server based changeable filters...

Sun Jan 12 16:23:51 EST 2003

Subject: Annoucement: Serverbased user changeable filters
From: "Roger Bille" <roger.bille at telia.com>
Date: Sat, 11 Jan 2003 10:32:23 +0100
X-Message-Number: 2

 Dear all,

 Introduction:
 The APRS-IS full feed today have a lot of traffic and require a high
bandwidth, in particular for the APRS-IS server sites, but also for some
=
of
you that connect that are only interested in the particular traffic. To
accommodate this a number of servers have special regional feeds which
filter the traffic. There are also some weather specific feeds
available.
But all these are setup according to what the server operator "thinks"
wi=
ll
be good for the users. Now we can take this one step further.

 Now will each of you be able to select what traffic you are interested
i=
n
and the server will create a unique feed for you. There is great
flexibil=
ity
to construct your personal feed.

 How does it work?
 Pete Loveall AE5PL have written the APRS-IS server software javAPRSSrvr
=
in
java which is used by a number of servers. Pete has been kind to create
s=
ome
hooks into his server software so I have been able to write a filter
add-=
on,
javAPRSFilter (also in java). These 2 applications work together to
provi=
de
this filtering. Status on the APRS-IS servers can be found here:
http://ahubswe.net/aprs_stat.asp

 You define the filter by doing the following:

	1. Connect and logon to a filter enabled port on a server
	2. Send an APRS message to the server requesting the filter you
want

 Filter commands
 There are 4 different kinds of filters that can be used in any
combinati=
on.
Each filter is working independent and is additive to the feed. This
mean=
 if
the filter finds a match it will be passed to you. The filter commands
in
the APRS message to the servers call is starting with the word 'filter'
(without quotes) and each filter command is delimited by a single space.
=
A
message with just 'filter?' (without quotes) will return the current
filt=
er
definition.

 #1 Range filter
 The range filter will pass all stations and their beacons, status,
messa=
ges
etc within a distance from a set location. It will also pass messages to
stations within the filter and positions of the message sender even if
th=
ey
are outside the range. Up to 3 range filters can be used at the same
time=
 to
extend the areas when you have problem to find a good circle match.

 Syntax:	r/lat/lon/dist [r/lat1/lon2/dist2 [[r/lat2/lon2/dist2]]

 Where:	r =3D range command
		lat =3D latitude in degrees (no decimals). Negative for
south
		lon =3D longitude in degrees (no decimals). Negative for
west
		dist =3D distance in kilometers from lat/lon.
			I'm sorry we don't use miles here in Sweden ;-)

 Samples:	r/55/-4/600		This will pass all traffic for
UK
		r/37/-81/1500	This will pass all east cost US traffic

 #2 Prefix filter
 The prefix filter will pass traffic based on if the sender=92s call
star=
ts
with a specific pattern. Up to 10 patterns can be defined at the same
tim=
e.

 Syntax:	p/p1/p2/p3... (up to 10)

 Where:	p =3D prefix command
		p# =3D The prefix (starting) pattern

 Samples:	p/K		This will pass all traffic from stations
starting with K
		p/SK/F	This will pass stations starting with either SK
or F
		p/SM5NRK	This will pass all traffic from SM5NRK
and any SSID at the end

 #3 Budlist filter
 The budlist filter will pass traffic based on exact match of the
sender=92=
s
call. Also the SSID is part of the exact match. If you want all SSID use
prefix filter above. Up to 10 calls can be defined at the same time (if
t=
hey
can fit in a single APRS message).

 Syntax:	b/call1/call2/call3... (up to 10)

 Where:	b =3D budlist command
		call# =3D The prefix (starting) pattern

 Samples:	b/SM5NRK		This will pass all traffic from
SM5NRK without any SS=
ID
		b/SM5NRK-5/SK5UM	This will pass all traffic from
SM5NRK-5 and SK5UM

 #4 Type filter
 The type filter will pass traffic depending on the packet type. More
tha=
n
one type can be defined in one single command.

 Syntax:	t/type

 Where:	t =3D type command
		type =3D is one or more of the following letters
			p =3D Position packets
			o =3D Objects
			i =3D Items
			m =3D Message
			n =3D NWS Weather
			w =3D Weather
			t =3D Telemetry
			q =3D Query
			s =3D Status
			u =3D User-defined

 Samples:	t/p		This will pass all traffic with a
position
		t/w		This will pass all weather traffic. For
positionless
				weather objects the corresponding
position packet
				will also be sent when it is next heard
		t/mos		This will pass all messages, objects and
status traffic

 Remeber that the APRS message must start with the word filter and the
th=
e
commands.

 The above filters can be combined as explain above. Each filter will
however working independent of the others, for example:

	filter r/63/16/1000 r/55/-4/600 p/F b/AE5PL t/s

 The above filter will pass all traffic within Nordic (range#1) AND UK
(range#2) AND stations starting with F (prefix) AND from AE5PL (budlist)
=
AND
all status traffic (type).

 Where to connect?
 This is up to each server operator if/when they will provide this type
o=
f
service. The following servers and ports have this enabled as far as I
kn=
ow.

	ahubswe.net:14580
	aprsca.net:14580
	aprseast.net:14580
	aprswest.net:14580

 I welcome any comments, suggestions and complains. I monitor the
UI-View
and APRSSIG lists.

 73 and have fun
 Roger Bille/SM5NRK

----------------------------------------------------------------------

---------
Darryl Smith, VK2TDS   POBox 169 Ingleburn NSW 2565 Australia
Mobile Number 0412 929 634 [+61 4 12 929 634 International] 
Darryl at radio-active.net.au | www.radio-active.net.au  

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