ipsvd is a set of internet protocol service daemons for Unix. It
currently includes a TCP/IP service daemon, and a UDP/IP service
daemon.

An internet protocol service (ipsv) daemon waits for incoming
connections on a local socket; for new connections, it conditionally
runs an arbitrary program with standard input reading from the
socket, and standard output writing to the socket (if connected),
to handle the connection. Standard error is used for logging.

ipsv daemons can be told to read and follow pre-defined instructions
on how to handle incoming connections; based on the client's IP
address or hostname, they can run different programs, set a different
environment, deny a connection, or set a per host concurrency limit.