[Xastir] Xastir on the Raspberry Pi

Thu Nov 14 15:40:19 EST 2013

I¹m going to try to take the linux AX25 description one step farther.
When you set up Linux AX25 ports and run ³kissattach², you are basically
creating a new network interface.  For example, when you run
/sbin/ifconfig on you RasPI, it shows two interfaces, eth0 and lo.  Mine
looks like this:

eth0      Link encap:Ethernet  HWaddr b8:27:eb:77:42:03
  inet addr:192.168.5.47  Bcast:192.168.5.255  Mask:255.255.255.0
  inet6 addr: 2601:0:XXXX:XXXX:XXXX:ebff:fe77:4203/64 Scope:Global
  inet6 addr: fe80::ba27:ebff:fe77:4203/64 Scope:Link
  UP BROADCAST RUNNING MULTICAST  MTU:7200  Metric:1
  RX packets:2649028 errors:0 dropped:0 overruns:0 frame:0
  TX packets:1305841 errors:0 dropped:0 overruns:0 carrier:0
  collisions:0 txqueuelen:1000
  RX bytes:2101471027 (1.9 GiB)  TX bytes:202355829 (192.9 MiB)

lo        Link encap:Local Loopback
  inet addr:127.0.0.1  Mask:255.0.0.0
  inet6 addr: ::1/128 Scope:Host
  UP LOOPBACK RUNNING  MTU:65536  Metric:1
  RX packets:33 errors:0 dropped:0 overruns:0 frame:0
  TX packets:33 errors:0 dropped:0 overruns:0 carrier:0
  collisions:0 txqueuelen:0
  RX bytes:2904 (2.8 KiB)  TX bytes:2904 (2.8 KiB)

(yes, I X¹ed out some of the IPv6 global address, no point in everyone
with an IPv6 connection connecting to my RasPi).
What kissattach and the AX25 utils do is use the KISS protocol to talk to
your TNC (like Curt described below) using standard Linux network sockets.
 Just like multiple programs can use your ethernet controller (I.e. You
can run a web server, stream some music, deliver mail, and connect to the
APRS-IS all over the same ethernet port), when you use Linux AX25 ports,
multiple programs can use the TNC at the same time, with the Linux kernel
handling things like contention and addressing.
So, once you run kissattach, you¹ll see this in addition to the other
ports when you run /sbin/ifconfig:
ax0       Link encap:AMPR AX.25  HWaddr N4NE-1
  inet addr:10.0.0.13  Bcast:10.255.255.255  Mask:255.0.0.0
  UP BROADCAST RUNNING  MTU:255  Metric:1
  RX packets:1264047 errors:0 dropped:0 overruns:0 frame:0
  TX packets:332975 errors:0 dropped:0 overruns:0 carrier:0
  collisions:0 txqueuelen:10
  RX bytes:96427373 (91.9 MiB)  TX bytes:26561785 (25.3 MiB)

Note that (in my case) it even has an IP address associated with it.  If I
were into self-pain, I could run TCP/IP over my 1200bps TNC and do things
like ³ping² and ³ssh² over that AX.25 interface.  You¹ll see that I also
have a ham call sign attached to the interface.  Everything that goes out
that port will do so as N4NE-1, so my other programs don¹t even really
need to know a call sign.

For APRS, what this means is that you can run APRX, Xastir, and even do
some ³beacon²s all using the same radio and Tnc at the same time, without
worrying about which one wants to transmit.  Also, all packets received on
the ax0 interface will go to ALL programs connected to it, at the same
time.

Hopefully that shines a little more light on a dark subject.

John Gorkos
AB0OO

On 11/14/13, 2:00 PM, "Curt, WE7U" <curt.we7u at gmail.com> wrote:

>On Wed, 13 Nov 2013, Max Harper wrote:
>
>> I have also been reading a little about AX.25 and at some point I think
>>I would like to have Xastir and APRX both running using AX.25. It's my
>>understanding that AX.25 makes the connection to the APRS-IS and the two
>>applications would use that connection, correct? Or is AX.25 only for
>>the TNC to be shared and each application still makes its own connection
>>to the
>>  APRS-IS?  Do packets also get passed between the two applications ?
>>What about when one application sends a packet to
>>  the TNC, does it also come back in to the other application? I'm
>>trying to get the big picture here as to how all this works
>>  together.
>
>Ok, I'll take a stab at the rest of your questions Tom didn't cover.
>
>AX.25 is not used for the APRS-IS connection.  It's used when talking to
>a TNC that is in KISS mode.  Or a soundcard device set up as a KISS port.
>
>What AX.25 will allow you to do is share a port across multiple bits of
>software.
>
>I'm not sure about the packets sent from one app to the TNC being seen by
>other apps.  Perhaps.  Give it a shot and see.
>
>As far as multiple connections to the APRS-IS servers:  If you run your
>own server locally, you can connect it to the APRS-IS, then connect all
>your other apps to your local server.
>
>Xastir does have server ports that you can enable, but they're not the
>full-service ports you'd find an JavaAprsServer or similar.  They're good
>for hooking multiple Xastir's together, possibly feeding off the same
>APRS-IS connection, but don't provide filtering.
>
>-- 
>Curt, WE7U.        http://wetnet.net/~we7u
>   "Lotto:  A tax on people who are bad at math." - unknown
>"Windows:  Microsoft's tax on computer illiterates." - WE7U.
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