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Hi Greg,<br>
<br>
Thanks for the feedback. My initial plan for validation of
IM->APRS messages is to take a similar approach to what Winlink's
APRSLink is doing: the APRS side user must pre-authorize the IM
user. This makes double sense in the XMPP case, because XMPP
already uses a mutual authorization protocol to add someone to your
roster. (Friend A says "I want to add friend B", and friend B must
accept the request before friend A can see presence information.)
This should be pretty effective against spam.<br>
<br>
I am curious what email gateway you are using. There are plenty of
them to send emails from APRS to the Internet, but I have yet to
find one that works well to send email from Internet to APRS.
Winlink's APRSLink can do it, but its lack of real-time
notifications to APRS makes it less than excellently useful.<br>
<br>
Integration with SMS might be possible down the road; it's a bit
trickier because the SMS gateways out there charge a fee, and the
email gateways aren't bidirectional (and could already be used
unidirectionally by one of the many email gateways out there.)<br>
<br>
Google Talk runs on a lot of smartphones and can achieve the same
effect, at least for those people that are already paying for
smartphone service.<br>
<br>
The other nice thing about this is that it works from desktops,
wifi, etc.<br>
<br>
-- John<br>
KR0L<br>
<br>
On 04/08/2012 01:25 PM, Greg Dolkas wrote:
<blockquote
cite="mid:CAHrzzAqprEkCD=n-NeoCR+mkg9g5xRBYq+MfZc+QcS9Lgd+fLg@mail.gmail.com"
type="cite">Hi John,<br>
<br>
Your last comment may be the most important... validating the
source of messages going from IM->APRS. I have totally
abandoned the Microsoft IM service because of the constant barage
of spam, virus-laden links, unsolicited buddy requests, etc. that
appear when I connect. Some of the other services are not much
better, and in my opinion, with the exception of Google's (which
is integrated in with their email service and so far spam-free),
nearly all are practically worthless to me these days. <br>
<br>
I've used the various APRS->Email gateways a number of times,
mostly successfully. With phone text messaging commonly used and
often more reliable and accessible than a phone call, and
email->text message gateways provided by all of the major
carriers, APRS->Phone Text Messaging can be an effective means
of communicating when I'm out of cellular range. <br>
<br>
The only trick to interoperating with a cell phone is to pick the
right ARPS email gateway so that the message comes across
formatted well for the phone. Some add additional information to
guide the person on the other end, and this isn't tolerated well
by some phones. (I crashed my daughter's Moto Razr once by doing
this...) Others end up with the message text as the subject,
etc. It can be quite confusing to the participants.<br>
<br>
So, if I might suggest, a better gateway to write would be for a
APRS->Phone Text Messge service. You'd need to use the
carrier's email-text gateways, but both are inherently
short-message based, so this should be quite effective if done
right. <br>
<br>
The biggest issue for both my preference and yours is the scarcity
of bi-directional iGates. Still useful for the "arrived safely"
messages, but not what I would like. Unfortunately, this is not a
software problem...<br>
<br>
Greg KO6TH<br>
<br>
<br>
<br>
<div class="gmail_quote">On Sun, Apr 8, 2012 at 10:24 AM, John
Goerzen <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:jgoerzen@complete.org">jgoerzen@complete.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid
rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left:
1ex;">
<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"
href="https://github.com/jgoerzen/ax25xmpp"
target="_blank">https://github.com/jgoerzen/ax25xmpp</a><br>
<br>
</div>
<br>
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