rns.recipes

Been lurkin this forum for a while, time to post something now :)

I'm dreaming of an interface to reticulum that could use SMS. You can get unlimited calling and SMS plans for quite cheap, even with prepaid, whereas unlimited data is more pricy. If you have one of those USB dongles that can do 2g/3g/4g/5g you can usually just send it AT commands and interface with it as you would with a regular modem.

My use case is to have a kiosk in a public space that can be used by anyone to send or receive messages, for the sake of simplicity let's ignore browsing nomadnet pages for a minute. The kiosk is equipped with a dongle. There's another device somewhere that's also equipped with a dongle and they can message between each other. Both SMS interfaces are set to access_point mode, otherwise the phone provider might ban you on the basis of fair use policy (usually m2m traffic is forbidden with a normal phone subscription), limiting the traffic will make it less likely to trip the systems of the phone provider.

If any of y'all are skilled with programming and looking for a little challenge I'll be very happy to test this in the next few weeks/months. Or maybe someone has already implemented this? Lemme know either way.

cheers
flok

That sounds cool! I've also been thinking about an SMS interface but unfortunately I am not good at programming right now. I considered an approach where someone could send messages through an SMTP/SMS gateway but have not had the time to seriously look into it.

Reticulum-->SMTP-->SMS SMS-->SMTP-->Reticulum

I thought about it from a network operator's perspective, as a way to use a phone and a cell plan to bridge networks using existing infrastructure. I also thought it would be a good way to have reliable, encrypted communication with my family members who are less interested in carrying LoRa devices with them everywhere they go.

SMS is not only an unencrypted payload, but the unsafest means of utilizing the cellular network in general. It's traffic can be easily intercepted and monitored, and when analyzed via heuristic methods, will quickly reveal to an adversary, be it the cellular operator or a third party, what types of payload is being transported. Also, SMS digestion/forwarding via GSM is very slow, unreliable. We are all trying to remove ourselves from the centralized, not funnel ourselves trough it, don't we? Even now you have TCP interface over cellular to communicate with people, that don't use LoRa.
You already have a modem interface in RNS, https://deepwiki.com/markqvist/Reticulum/4.6-serial-kiss-and-ax.25-interfaces.

why are you so opposed to fun, aether?

Why are you so opposed to reason, holistic?
If you find what I wrote incorrect or unreasonable, please reason why this is so, objectively. Otherwise, such questions are meaningless and purely provoking.

Couple of months ago I was looking at doing Reticulum over InReach satellite text messages, and in end decided that it wouldn't be practical. InReach messages are so small that you'd need 2 to send an announce, or 5 to send one regular Reticulum packet at 500b MTU. And at 1 message per 10 minutes, that didn't sound reasonable.

And so I ended up doing custom chunking to get GRIBs through InReach.

SMS might have similar limitations.

@aetherlab you're totally right on the limitations of sms. I'd still like to see that interface happen. The modem interface "documentation" you linked is not for AT modems.

@bergie - yeah seems like a hassle, also probably really expensive to use Iridium for this. SMS though has an MTU of 1120 bits (https://en.wikipedia.org/wiki/SMS#Message_size) and allows for sending arbitrary binary data. Also you can concatenate the messages which basically tells the network to expect multiple packets/messages as part of one transmission.

I read online that it's possible with some Android devices to use them as AT modems as well, I'm rooting a spare smartphone I have lying around to see that for myself. Will report back when I have some results. :)

flok wrote:

@aetherlab you're totally right on the limitations of sms. I'd still like to see that interface happen. The modem interface "documentation" you linked is not for AT modems.

Oh yes, true. Some additional development will be necessary. But anyway, SMS itself will nee some too, to work, with 140 bytes of payload size.

ok so update is, I connected a smartphone (galaxy a5y17, rooted) to my laptop and it shows up as /dev/ttyACM0 and I can minicom into it and send it raw AT commands and send SMS that way. It is quite flaky and sometimes it stop responding alltogether and I have to reboot the phone to get it working again. But that's just an implementation problem, I'll test this soon with some other devices and see what the results are.
Also, I cannot read any incoming messages as none are listed after running AT+CMGL="ALL". My suspicion is that the OS automatically pulls them into storage and deletes them from the modem memory. I tried disabling acess for all apps to messages but that didn't do anything. In any case this shouldn't be a problem with a usb dongle. So it seems like implementing this should be trivial.

Ive done it over a SIMCOM SIM7028 NBIOT 20kbps connection. Wrote a pipe interface for it that uses AT commands. It has a transparent mode so its basicly a dialup modem you point at a tcp server, roblem is you need an NBIOT sim for it, prices are $15-20 AU p/m for 500mb of data, bit more for a gb. I planned to use it for lora backhaul. There is a SIM7080 module that i think can do SMS though. Using internal interfaces keep the data costs down but you would never use it for a full transport node. When the cardputer zero is avaiable and i can get the sim7080 module they also sell i was thinking it might make a good handheld. There are a few advantages to using the simcom modems, they run over serial so they are isolated. etc.

interfaces need links for reticulum to work unless you want so send only announces. how do you keep a fixed link with sms or other temporary connetions?

being able to use a dialup modem would be interesting. there is a lot of old but usable equipment laying around and telephone lines are still viable in some parts of the world.

I'm just not into inserting random dongles into my devices

I think you can just use paper messages. Send it via sms to your friend. And he can easily decode it in meshchatx or sideband.

i'm putting this on the backburner for now, busy with other things. But since both older phone modems and modem cellurar modems use AT commands you could kill two birds with one stone if an AT interface gets implemented.