Re: [aprsisce] Tricks with IS-Server Port Filters
- Snazzy... and only available to APRSISCE/32 users too!
WF5XOn Fri, Jul 29, 2011 at 5:08 PM, Lynn W Deffenbaugh (Mr) <kj4erj@...> wrote:
Ok, here's an advanced topic for those of you that understand netmasks,
telnet, APRS-IS server, and filters.
Consider the following filter (Note that this is only supported by
APRSISCE/32, not the general APRS-IS server):
What do you think that would do? If you guessed that it would give you
all the packets received on an RF port and exclude all packets received
via APRS-IS, you'd be correct. You can see this with Control-G
(FilterTest) and enter that filter, a handy way to get a window that
shows the RF-received packets, and ONLY the RF-received packets (well,
with a bit of filter-cruft at the front of each line).
Now, what good is that information? Well, have you ever wanted a way to
remotely see what packets your IGate is hearing? Real-time and without
any APRS-IS duplicate filtering? Here's how:
1) Configure a local IS-Server port in your IGate instance. It'll be
TCP/IP on 0.0.0.0 on an available port of your choosing. (If you want
it to only work from the same machine, use 127.0.0.1. If you want it to
work only from your LAN, use the IP address of that machine on your
LAN. 0.0.0.0 will accept inbound connections from any IP address like
from the Internet if your firewall allows it, remember to open the port
you've chosen.) (This is the part that requires you to understand
netmasks and ports and binding of sockets to ports).
2) From any machine that has access to the IP address you gave to the
IS-Server port, telnet to that server and port. For command-line
telnet, the command would be "telnet IPAddress Port" for example, for me
to connect to APRSISCE on my WiFi-connected phone instance which is
listening on port 14580, I'd use "telnet 192.168.10.187 14580". (This
is the part that wants you to understand telnet).
3) Enter the APRS-IS logon string like "user YOURCALL-SSID pass -1" and
hit enter. Of course, use your own callsign-SSID (nearly any -SSID will
work since APRSISCE/32 doesn't reject duplicate connections). The
password is required by doesn't need to be valid for the callsign
because we're just going to listen anyway. After this, you should start
getting heartbeats from the server.
4) Enter the filter above with the command "#filter b/* -e/*" and hit
enter. You should now start receiving all RF-received (non-APRS-IS)
packets from your IGate!
How does this work? b/* says to make the whole world your buddy and get
all packets (APRS-IS requires at least one character before the *,
APRSISCE/32 supports total wildcards). The e/ filter is the "entry"
filter that checks the path component following the qA construct. The *
again matches any station doing the entry and the leading minus (-)
makes that filter term an exclusion clause.
Yes, you can monitor your IGate's RF reception from anywhere that can
connect to the IGate's port. Pretty powerful, huh?
Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32