services – Internet network services list
cat /etc/services
services is a plain ASCII file providing a mapping between friendly textual names for internet services, and their underlying assigned port numbers and protocol types. Every networking program should look into this file to get the port number (and protocol) for its service.
A sample services file might look like this:
-
netstat 15/tcp qotd 17/tcp quote msp 18/tcp # message send protocol msp 18/udp # message send protocol chargen 19/tcp ttytst source chargen 19/udp ttytst source ftp 21/tcp # 22 - unassigned telnet 23/tcp