NNCP uses asynchronous communication, so the source and destination need never be online simultaneously. NNCP can route requests via intermediate devices – other NNCP nodes, USB sticks, tapes, radios, phones, cloud services, whatever – leading to a network that is highly resilient and flexible. NNCP makes it much easier to communicate with devices that lack Internet connectivity, or have poor Internet. NNCP is to UUCP what ssh is to telnet; NNCP is an Encrypted, authenticated, onion-routed version of UUCP"

https://www.complete.org/nncp/