Or resurrect a modified form of FIDONet and dust off the old BBS software. Point-to-point dial ups with mobile phones are hard to shut down unless you crash the entire phone system. Communications aren't instantaneous, but you can get the messages moving around the world within 48 hours. Problem with being a technophile, you don't know what to do when the backbone crashes or the DNS server is shut down. Most modern technophiles couldn't tell you where 127.0.0.1 will take you, or what you'll see, or even how to enter it. You'll have to go old school, like BBS's and IRC.
HAM radio works pretty well for message traffic. Hook up a laptop to a transceiver, find a frequency and you can transfer data the same way you would with landlines.
Trouble is that you have to have a listener, but with a functional communications network, that won’t be a problem.