/usr/bin/systemd-socket-activate

> systemd-socket-activate [OPTION…] COMMAND…

Listen on sockets and launch child on connection.

Options:
  -h --help                  Show this help
     --version               Show package version
  -l --listen=ADDR           Listen for raw connections at ADDR
  -d --datagram              Listen on datagram instead of stream socket
     --seqpacket             Listen on SOCK_SEQPACKET instead of stream socket
  -a --accept                Spawn separate child for each connection
  -E --setenv=NAME[=VALUE]   Pass an environment variable to children
     --fdname=NAME[:NAME...] Specify names for file descriptors
     --inetd                 Enable inetd file descriptor passing protocol
     --now                   Start instantly instead of waiting for connection

Note: file descriptors from sd_listen_fds() will be passed through.

See the systemd-socket-activate(1) man page for details.