I loaded up this title with buzzwords. The basic idea is that IM systems shouldn’t have to only use the Internet. Why not let them be carried across LoRa radios, USB sticks, local Wifi networks, and yes, the Internet? I’ll first discuss how, and then why.

How do set it up

I’ve talked about most of the pieces here already:

• Delta Chat, which is an IM app that uses mail servers (SMTP and IMAP) as transport, and OpenPGP encryption for security.
• One of the items I highlighted in Tools for Communicating Offline and in Difficult Circumstances, such as:
  • NNCP, which I have talked about a lot. NNCP can run atop a network, over USB drives (sneakernet) (even airgapped), and over many other transports.
  • Syncthing, which can form an ad-hoc mesh.
  • Filespooler, which handles remote command execution, and can use a transport such as Syncthing or NNCP to get messages to their destination.
  • Yggdrasil, which forms an auto-mesh network over things like ad-hoc wifi. It’s not asynchronous itself, but its properties may be used to build an asyncrhonous email network – email itself can be asynchronous across any carrier. Others such as Tor could also be used.
  • And various other physical carriers such as LoRa and XBee SX radios.
• Email servers. For instance, there are existing instructions for running Postfix or Exim over NNCP. These can be easily adapted to run across something like Filespooler instead. These can be run locally on a laptop, or, with a tool such as Termux, on Android.

So, putting this together:

• All Delta Chat needs is access to a SMTP and IMAP server. This server could easily reside on localhost.
• Existing email servers support transport of email using non-IP transports, including batch transports that can easily store it in files.
• These batches can be easily carried by NNCP, Syncthing, Filespooler, etc. Or, if the connectivity is good enough, via traditional networking using Yggdrasil.
  • Side note: Both NNCP and email servers support various routing arrangements, and can easily use intermediary routing nodes. Syncthing can also mesh. NNCP supports asynchronous multicast, letting your messages opportunistically find the best way to their destination.

OK, so why would you do it?

You might be thinking, “doesn’t asynchronous mean slow?” Well, not necessarily. Asynchronous means “reliability is more important than speed”; that is, slow (even to the point of weeks) is acceptable, but not required. NNCP and Syncthing, for instance, can easily deliver within a couple of seconds.

But let’s step back a bit. Let’s say you’re hiking in the wilderness in an area with no connectivity. You get back to your group at a campsite at the end of the day, and have taken some photos of the forest and sent them to some friends. Some of those friends are at the campsite; when you get within signal range, they get your messages right away. Some of those friends are in another country. So one person from your group drives into town and sits at a coffee shop for a few minutes, connected to their wifi. All the messages from everyone in the group go out, all the messages from outside the group come in. Then they go back to camp and the devices exchange messages.

Pretty slick, eh?

Note: this article also has a more permanent home on my website, where it may be periodically updated.