*** John Goerzen [2020-12-26 23:03]:
>Yes, I know this feeling.  I have been working on software for running over
>long-distance, low-power, low-bandwidth wireless links (think 10-30 miles /
>15-50 km with <1W).

You know, *the most* impressive, the most delightful time in my life was
using modems, COM-ports, BBSes and FidoNet. I really love all that
technologies, all that magic. Unfortunately I deal only with ordinary
modems (and bad telephone lines) and only read about *X.25 and similar
things. Possibly that is just because I was young school pupil
fascinated with everything related to computers. However that was
beginning of 2000-s where BBS/FidoNet world mostly was considered dead.

>- I can just run PPP with VJ header compression across this thing  and it's
>maybe less efficient but good enough.

Same thoughts visited me too. When I connected my two server via
COM-cable (FreeBSD 12.x, modern ones, Xeon-inside and so on :-)), I
stayed with PPP setup -- simple and pretty good enough, especially on
that network delays.

>I was surprised that I couldn't find any general-purpose library or tool for
>doing this.  ZModem & friends aren't general-purpose enough for what I want
>(and probably not for what you want either).

Exactly! I was disappointed with that fact too.

>for "reliable framing protocol serial" and found
>https://github.com/BaroboRobotics/libsfp which I need to look into more.

Well, creating just reliable framing protocol is not hard (XMODEM with
better checksums is still here :-)), in my opinion. But doing that
effectively with sliding windows, FECs and knowing that there are huge
science work on all of that -- becomes much more complicated frightening task.

-- 
Sergey Matveev (http://www.stargrave.org/)
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