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How computers are identified on the Internet
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Well-known ports
Following are some of the most common well-known ports.
How computers are identified on the Internet
Millions of computers are connected to the Internet. When you are trying to
identify computers, it is easier to work with groups of computers rather
than having to identify each one individually. Subnet masks provide a way
to identify a group of related computers, such as those on your local
network.
Default port Service name Program
20 ftp-data FTP (File Transfer Protocol) data
21 ftp FTP (File Transfer Protocol) control
23 telnet Telnet terminal handler
25 smtp SMTP (Simple Mail Transfer Protocol)
53 domain DNS (Domain Name Service) lookup
79 finger Finger
80 http HTTP (Hypertext Transfer Protocol)
110 pop3 POP3 (Post Office Protocol 3)
113 auth Ident Authentication Service
119 nntp NNTP (Network News Transfer Protocol)
137 nbname NetBIOS name (Microsoft Networking)
138 nbdatagram NetBIOS datagram (Microsoft
Networking)
13 9 nbsession NetBIOS session (Microsoft Networking)
143 imap IMAP (Internet Message Access Protocol)
19 4 irc IRC (Internet Relay Chat)
389 ldap LDAP (Lightweight Directory Access
Protocol)
443 https HTTPS (Secure HTTP)