remote TNC

remote TNC

[Hamish Moffatt]

Hi all,

Merry Christmas.

Can anyone suggest solutions for using an AX.25 port (TNC, soundmodem
or whatever) remotely eg hooked up to a different computer. Here's two 
scenarios:

1. Computer A wants to transmit/receive on RF; RF port is attached to
   computer B; computers are on a local Ethernet together.

   +------------+          +------------+
   | Computer A |----------| Computer B +-- RF port (TNC etc)
   +------------+ Ethernet +------------+
     Runs application        Has RF port
     eg XASTIR

   Computer A wants to work through B transparently;
   it wouldn't have to specifically mention B in its AX.25 packet path,
   nor would frames received back by B.

2. Same but computers are connected only via IP, not necessarily on
   the same Ethernet:

   +------------+          +--------+           +------------+
   | Computer A |----------+ Router +-----------| Computer B +-- RF port
   +------------+ Ethernet,+--------+ Ethernet, +------------+
                  PPP etc.            PPP etc.
     Runs application
     eg XASTIR

   Again the application on A would like to see a standard Linux
   networking interface and think it's connected directly to RF.

On a related note, can somebody give me a good description (either here
or a URL for) for BPQ over Ethernet? Is that part of the answer to #1?
I think AX/IP (RFC 1226) is the protocol behind #2, but does linux (ie
ax25ipd) do this already?


Thanks,
Hamish
-- 
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>

Re: remote TNC

[Tomi Manninen]

On Thu, 26 Dec 2002, Hamish Moffatt wrote:

> 1. Computer A wants to transmit/receive on RF; RF port is attached to
>    computer B; computers are on a local Ethernet together.
> 
>    +------------+          +------------+
>    | Computer A |----------| Computer B +-- RF port (TNC etc)
>    +------------+ Ethernet +------------+
>      Runs application        Has RF port
>      eg XASTIR
> 
>    Computer A wants to work through B transparently;
>    it wouldn't have to specifically mention B in its AX.25 packet path,
>    nor would frames received back by B.

This would be a case for BPQ ether and rxecho I think. You can make it 
so that A has a TNC directly connected to it.

> 2. Same but computers are connected only via IP, not necessarily on
>    the same Ethernet:
> 
>    +------------+          +--------+           +------------+
>    | Computer A |----------+ Router +-----------| Computer B +-- RF port
>    +------------+ Ethernet,+--------+ Ethernet, +------------+
>                   PPP etc.            PPP etc.
>      Runs application
>      eg XASTIR
> 
>    Again the application on A would like to see a standard Linux
>    networking interface and think it's connected directly to RF.

Here you will have to use AXIP but I think you can still get the same as 
in hte above with rxecho.

> On a related note, can somebody give me a good description (either here
> or a URL for) for BPQ over Ethernet? Is that part of the answer to #1?
> I think AX/IP (RFC 1226) is the protocol behind #2, but does linux (ie
> ax25ipd) do this already?

Ax25ipd does RFC 1226, yes. For bpq ether I don't know about a good 
description. But it is simply AX25 over raw ethernet, so there is not much 
to it. The bpqparms(8) man page tells you pretty much everything needed to 
configure it.

-- 
Tomi Manninen           Internet:  oh2bns@sral.fi
OH2BNS                  AX.25:     oh2bns@oh2rbi.fin.eu
KP20ME04                Amprnet:   oh2bns@oh2rbi.ampr.org

Re: remote TNC

[Tomi Manninen]

On Wed, 25 Dec 2002, Tomi Manninen wrote:

> This would be a case for BPQ ether and rxecho I think. You can make it 
> so that A has a TNC directly connected to it.

Argh... I meant that it can be configured so that A _thinks_ it has a TNC
connected directly to it...

-- 
Tomi Manninen           Internet:  oh2bns@sral.fi
OH2BNS                  AX.25:     oh2bns@oh2rbi.fin.eu
KP20ME04                Amprnet:   oh2bns@oh2rbi.ampr.org

Re: remote TNC

[Øyvind Hanssen]

I have also been thinking about this, specifically, I was thinking
about using Xastir on my laptop while the radio was running on 
another computer. 

I modfied the aprs_tty program by PE1DNN to use stdin/stdout
instead of a pty. Then I was able to use ssh to run this on the
computer with the radio and redirect i/o to the other end. I believe
it is possible to redirect the client end of ssh to a pty such that
Xastir can connect it. I havent managed to get it working yet
but it should not be too hard. 

Better though, I believe one could modify Xastir to fork off 
an external command and redirecting is i/o to a pipe etc. etc.

Of course, axip is a more generic solution, but with Xastir we
need the aprs_tty program anyway (if not running Xastir as root). 

73 de LA7ECA, Øyvind 

> Here you will have to use AXIP but I think you can still get the same as
> in hte above with rxecho.
[...]
-- 
Associate Professor, Computer Science dept., University of Tromsø
oyvind@cs.uit.no, http://hans.priv.no/oivindh
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