Three-point VPN Gateway. WireGuard, IPTables/NFTables, DNS, dnsmasq. VPN server and Internet gateway on different machines.

ZeroMQ async messaging. Can run brokerless. Runs on top of ITC, IPC, PGM, TCP, TIPC, UDP, or VMCI. BSD sockets-like API. REQ-REP, PUB-SUB, and PUSH-PULL pattern.

Physical one-way data link. 100Mbps ethernet + UDP/IP. File transfer with ncat or socat and tar.