[OZAPRS] Server based changeable filters...
Darryl at radio-active.net.au
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
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
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
But all these are setup according to what the server operator "thinks"
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
and the server will create a unique feed for you. There is great
to construct your personal feed.
How does it work?
Pete Loveall AE5PL have written the APRS-IS server software javAPRSSrvr
java which is used by a number of servers. Pete has been kind to create
hooks into his server software so I have been able to write a filter
javAPRSFilter (also in java). These 2 applications work together to
this filtering. Status on the APRS-IS servers can be found here:
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
There are 4 different kinds of filters that can be used in any
Each filter is working independent and is additive to the feed. This
the filter finds a match it will be passed to you. The filter commands
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.
message with just 'filter?' (without quotes) will return the current
#1 Range filter
The range filter will pass all stations and their beacons, status,
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
are outside the range. Up to 3 range filters can be used at the same
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
lon =3D longitude in degrees (no decimals). Negative for
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
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
with a specific pattern. Up to 10 patterns can be defined at the same
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
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
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
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=
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
one type can be defined in one single command.
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
t/w This will pass all weather traffic. For
weather objects the corresponding
will also be sent when it is next heard
t/mos This will pass all messages, objects and
Remeber that the APRS message must start with the word filter and the
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)
all status traffic (type).
Where to connect?
This is up to each server operator if/when they will provide this type
service. The following servers and ports have this enabled as far as I
I welcome any comments, suggestions and complains. I monitor the
and APRSSIG lists.
73 and have fun
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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