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A TCP or UDP port with a number in the range 0-1023 (originally 0-255). The well-known port numbers are assigned by the IANA and on most systems can only be used by system (or root) processes or by programs executed by privileged users.
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well-known portA number from 0 through 1023 used to identify a network service on a private IP network or the public Internet. Residing in a field in the TCP or UDP header, the port number directs packets to the appropriate application in the server. The most common well-known port is 80, which identifies HTTP traffic for a Web server (see port 80). For details about port numbers, see TCP/IP port.
Registered and Private Ports
The Internet Assigned Numbers Authority (IANA) registers ports 1024 to 49151 for the convenience of the Internet community. Port numbers from 49152 to 65535 are private ports, also called "dynamic ports." For the complete list of well-known ports and registered ports, visit www.iana.org/assignments/port-numbers. See port scanning, ICANN and IANA.
COMMON WELL-KNOWN PORTSService Port Function HTTP 80 Web HTTPS 443 Web (secure) FTP 20,21 File transfer SFTP 22 File transfer (secure) FTPS 989,990 File transfer (secure) SIP 5060 VoIP (Internet phone) DNS 53 Find IP address SMTP 25 Internet mail POP3 110 POP mailbox IMAP 143 IMAP mailbox Telnet 23 Remote login SSH 22 Remote login (secure) NNTP 119 Usenet newsgroups NNTPS 563 Usenet (secure) IRC 194 Chat NTP 123 Network time of day SNMP 161,162 Network management CMIP 163,164 Network management Syslog 514 Event logging Kerberos 88 Authentication NetBIOS 137-139 DOS/Windows naming
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