How to organize network (Internet) communication between devices, WITHOUT IP?

Question

mesh

Gentlemen, I have a basic understanding of Networks, but I have never encountered such a task,
and no solution comes to mind right away, while I am sure that there are ready-made solutions.

Task: there are many, many devices scattered around the world (let there be IoT).
The system is decentralized (i.e. there is no "master" server).
Each device can be assigned its own unique ID.

Question:
How to organize a connection between them so that each of the devices, specifying the ID of the other,
can contact it?
Through IP - will not work, they can connect to the Internet in different places,
and even if they manage to bind to IP - 99% that it will be a dynamic address.
(and, I suspect/I'm afraid that since there is no IP, then the DNS server system will not be able to be used either?)
(but how then? I don’t want to send a broadcast request to thousands of devices around the world ..)

//and just in case: nothing I don't think bad. This is not a bot, no, or some other idea to spoil someone)

Answer 1

Absolutely without IP - in any way.
And so it is possible that the devices scan the entire Internet for the presence of each other. When the ip and ports of each other are clarified, then it is already possible to pull encrypted channels, etc. Those devices that have white (dedicated) ip can take on the role of temporary servers and coordinate the rest. Something like this.
DNS is practically not needed at all. It's for people, not devices. But if you use it as an ip registration system, then there is a benefit, but then the decentralization condition is violated. If we stir up coordination through the server, then there are other solutions besides dynamic dns.

Answer 2

Well, we got out of this situation by raising our VPN server ...
you can try it in the way that IP cameras connect ... it's like p2p by IDs ... but I didn't figure it out. who vkurse - throw off the server / client where to dig)

Answer 3

See how the networks used by cryptocurrency node applications and torrent clients work, see how dht is implemented
Exit nat using upnp, when using udp, you can connect to a 'foreign' channel. Each device must keep a list of the latest id:ip:port for each device or subset sufficient for connectivity, each device, when entering the network, updates information about itself and downloads prompt updates from others.
Someone should issue the initial list of ip addresses for anyone, using either a brutally clogged domain in the client, where the first node will be guaranteed to be launched, in fact, through dns, the initial list of nodes is called dnsseed, and later this main node can be closed, and ip addresses in dns issue about permanent hosts
upd. .. or ask the user, for example, to connect to the network, a working node must issue an 'invite', for example, in the form of a qr-code, which will contain the address of this node.
In the local network, you can search for working nodes by broadcasting or brute force search of addresses; for mailings, the node must listen to them accordingly.