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Definition: well-known port

A 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.


 Service   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