Ports and Ports Numbers

One host computer can run more than one server program. For example, a small ISP might have one computer running a POP server, SMTP server, web server, and news server. To keep requests for information straight, each type of server responds to packets sent to specific ports (input for a specific Internet service). Ports are numbered, and standard port numbers used throughout the Internet. almost never need to type port numbers, but here are some widely used port numbers in case you do:

Port Number                                                 Internet Service

21                                                                                                     FTP (file transfer)
23                                                                                                    Telnet (remote login)
25                                                                                                    SMTP (mail relaying)
80                                                                                                    World Wide Web
110                                                                                                  POP3 (storage of incoming mail)
194 (as well as 6667 and many others)                                          IRC (online chat)
532.                                                                                                 Usenet newsgroups

For a complete listing of port numbers, see the IANA.