[Xastir] hit and run packet

[Wes Johnston]

Not to prolong this thread about UDP, but hey, I had a neat-o idea.

As I drive down the street, my WLAN card is scanning... a-la netstumbler.  If it
found a non-wep AP nearby, it could attach automatically.  A script running in
the background checking the eth0 IP address would see that the eth0 IP address
was no longer 0.0.0.0, and would begin to send APRS formatted lines of text to
a copy of xastir I had running at home via UDP packets.  As my car moved out of
range of the AP and resumed scanning, the scipt would see the eth0 address blank
out, and would stop sending the one liners of text.

Previously I'd thought of using 802.11 at my home or EOC or TOC to SEND UDP
packets.  Now I'm thinking that I could use UDP packets transmitted from my
mobile station to quickly utilize ANY 802.11 open AP.

Now for something a little different.....use TCP/telnet connections....(this is
def a seperate app on the server side... too much going on in this suggestion
to stuff into xastir... but javaaprs is a thought.)

Darryl Smith http://www.radio-active.net.au/web/tracking/gprs.html had a page at
one time (I can't locate the extact text now), that involved a special telnet
connection that kept track of the last packet a particular user received. 
Then, as you reconnected (this was all with GSM phones), it would quickly catch
you up from the last packet you received.  I could see that it would be
necessary to keep a cache of packets listed by callsign.  No sense in sending
old locations to the user when he reconnects, esp if he'll only be connected
for the seconds that he would be over 802.11b in a car.  And of course this
would have to time out too... we wouldn't want to queue too many packets... so
arbitrarily, let's say it's 30 minutes.

Let's say you are within range of an AP.  You get an IP address, and telnet in
to "any given aprs internet server".  First thing that happens upon connection
to that telnet server is you send your callsign at the callpass hash.  The
telnet server now knows your callsign and has associated it with the socket you
are connected on.  You now have a two way link with the APRS IS data stream via
the random AP you happen to be driving past.  If you wandered out of range of
the AP, your connection would fail.  The APRS Telnet server would realize that
the user at _that_ socket was unreachable, and mark that point in time.  From
that point on (up to say, 30 minutes), a list of all packets you are missing is
kept.  Well, not all packets, just the _last_ packet of each type... posit,
status, etc from each station heard by the telnet server.  When your WIFI card
drives past the _next_ random AP, it connects to the server again, and the
telnet server catches you up... similar to the "last 30minutes" you get when
connecting to some aprs telnet server ports... similar, but customized for YOUR
CALLSIGN.... so it wouldn't be as much data as the last 30 minutes... it would
be only what YOU missed.

All that's needed on the xastir side is for xastir to sense the connection
station of the eth0 {or eth1/2/3/4) card and try to reconnect to the normal
internet server ASAP when a connection exists on the network card.

Wes