Building an Asynchronous, Internet-Optional Instant Messaging System

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:

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.

26 thoughts on “Building an Asynchronous, Internet-Optional Instant Messaging System

  1. @jgoerzen I keep being annoyed that when I want to use my phone as a short range walkie talkie in the house, we both need to connect to the Internet and talk to each other through a server. It feels like the two devices should be able to discover and just talk to each other directly in things like Signal, Meet, etc. … alas.


  • Devin
  • Floris Bruynooghe
  • Matt W1CDN
  • Neal Walfield

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