inetd

inetd (internet service daemon) is a super-server daemon on many Unix systems that provides Internet services. For each configured service, it listens for requests from connecting clients. Requests are served by spawning a process which runs the appropriate executable, but simple services such as echo are served by inetd itself. First appearing in 4.3BSD, it is generally located at /usr/sbin/inetd. inetd is based on the (service) activator pattern