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Thanks John. I've browsed the source and it looks helpful. Much
appreciated.<br>
<br>
-- John<br>
<br>
On 04/08/2012 03:47 PM, John Gorkos wrote:
<blockquote cite="mid:CBA74FC4.4AB8%25jgorkos@gmail.com" type="cite">
<div>Please review the code found here:</div>
<div><a moz-do-not-send="true"
href="https://github.com/ab0oo/javAPRSlib">https://github.com/ab0oo/javAPRSlib</a></div>
<div>The multi-part message capability isn't in there, but the
ability to encode and decode messages is.</div>
<div>Let me know if you'd like any help implementing or testing.</div>
<div><br>
</div>
<div>John Gorkos</div>
<div>AB0OO</div>
<div><br>
</div>
<span id="OLK_SRC_BODY_SECTION">
<div style="font-family: Calibri; font-size: 11pt; text-align:
left; color: black; border-width: 1pt medium medium;
border-style: solid none none; border-color: rgb(181, 196,
223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in
0in;"><span style="font-weight: bold;">From: </span> John
Goerzen <<a moz-do-not-send="true"
href="mailto:jgoerzen@complete.org">jgoerzen@complete.org</a>><br>
<span style="font-weight: bold;">Reply-To: </span> TAPR APRS
Mailing List <<a moz-do-not-send="true"
href="mailto:aprssig@tapr.org">aprssig@tapr.org</a>><br>
<span style="font-weight: bold;">Date: </span> Sun, 08 Apr
2012 12:24:29 -0500<br>
<span style="font-weight: bold;">To: </span> <<a
moz-do-not-send="true" href="mailto:aprssig@tapr.org">aprssig@tapr.org</a>><br>
<span style="font-weight: bold;">Subject: </span> [aprssig]
APRS message-handling algorithms / libraries<br>
</div>
<div><br>
</div>
<div>
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<div bgcolor="#ffffff" text="#000000"> Hi folks,<br>
<br>
I am looking to write some APRS software, and I'm hoping to
avoid re-inventing the wheel. I am particularly interested
in libraries in any cross-platform language (C, Perl,
Python, Java, etc.) that can be used to receive and generate
APRS messages.<br>
<br>
In my research, there are quite a few libraries that receive
APRS messages, but I have found none that are helpful with
generating them. This seems to be something with some
complexity; such as:<br>
<ul>
<li>Splitting data up into packets of the appropriate size
(APRSLink for Winlink appears to somehow detect the type
of device in use and generates shorter messages for
TH-D7A. Anyone know how to do this, and what are the
appropriate sizes for the D7A, D72A, 710, and VX-8GR?)</li>
<li>Processing/generating ACKs, REJs, etc.</li>
<li>Proper timing for retransmit of packets that weren't
ACKed.</li>
</ul>
None of this is hugely complicated, and the APRS spec is
fairly clear on the ACK, REJ, etc. process. The maximum
message sizes appear to be undocumented and I'm hoping
someone can help me out there.<br>
<br>
My project, incidentally, is to build a bidirectional
APRS-XMPP bridge. XMPP is the protocol behind the instant
messaging tools such as Jabber and Google Talk, and is
available for free on every modern platform. In the spirit
of both amateur radio and the Free Software communities I'm
a part of, full source code to this project will be
available. I actually already wrote a much simpler piece of
related software, letting someone take a connected AX.25
session and bridge it to XMPP, [1] so I do have some
experience under my belt. This is obviously a more complex
project, but XMPP looks like an excellent way to bridge APRS
to other systems. I think it is a better fit than the email
gateways out there, and in fact, XMPP already has fields for
carrying presence information and location information with
presence packets.<br>
<br>
Are there any particular notes available to those
implementing gateways between APRS and non-APRS sources? I
have taken note of what sites such as OpenAPRS or Winlink do
to validate people for access, and plan to do something
similar here.<br>
<br>
Thanks,<br>
<br>
-- John<br>
KR0L<br>
<br>
[1] source code at <a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="https://github.com/jgoerzen/ax25xmpp">https://github.com/jgoerzen/ax25xmpp</a><br>
<br>
</div>
</div>
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