Secure UUCP-like store-and-forward exchanging.
This utilities are intended to help build up small size (dozens of nodes) ad-hoc friend-to-friend (F2F) statically routed darknet delay-tolerant networks for fire-and-forget secure reliable files, file requests, Internet mail and commands transmission. All packets are integrity checked, end-to-end encrypted, explicitly authenticated by known participants public keys. Onion encryption is applied to relayed packets. Each node acts both as a client and server, can use push and poll behaviour model.
Out-of-box offline sneakernet/floppynet, dead drops, sequential and append-only CD-ROM/tape storages, air-gapped computers support. But online TCP daemon with full-duplex resumable data transmission exists.