Primary TCP/IP Port Assignments and Descriptions
TCP/IP provides a total of 65,535 ports of which 1023 are considered to be well known ports. In reality the number of ports that are used by popular network clients and services comprises an even smaller subset of the well known group of ports. The following table lists the functions of this subset.
| Port | Assigment | Description |
|---|---|---|
| 20 | FTP | File Transfer Protocol (Data) - The File Transfer protocol provides a mechanism for transferring specific files between network connected computer systems (usually a Linux or UNIX based system). Transfer is typically performed using the ftp client which provides a range of commands used to connect to a remote server for the purpose of uploading or downloading files. Most modern web browsers also have the ability to browse and download files located on a remote FTP server. FTP uses TCP (rather than UDP) to transfer files so is considered to be a highly reliable tranport mechanism. |
| 21 | FTP | File Transfer (Control) - Traditionally FTP has two ports assigned (port 20 and port 21). Port 20 was originally conisidered the data transfer port, while port 21 was assigned to communicate control information. In modern implementations port 20 is now rarely used, with all communication taking place on port 21. |
| 22 | SSH | Secure Shell - The Secure Shell is used to provide a secure, encypted, remote login to session top a remote host over a TCP/IP network. This essentially provides a mechanism to log into a remote system. The original mechanism for remotely terminal access was the Telent protocol. Because Telnet transmits everything in plain text its use is now strongly discouraged in favor of the secure shell, which encrypts all communications, including log-in and password credentials. SSH also provides the mechanism by which files can be security tranfered using the scp client. SSH also now replaces both the rsh and rlogin clients. |
| 23 | Telnet | |
| 25 | SMTP - Simple mail Transfer Protocol | |
| 53 | DNS - Domain Name Server | |
| 69 | TFTP - Trivial File Transfer (UDP based) | |
| 80 | HTTP - Hypertext Text Transfer Protocol | |
| 110 | POP3 - Post Office Protocol | |
| 119 | NNTP - Network News Transfer Protocol | |
| 123 | NTP - Network Time Protocol | |
| 143 | IMAP4 - Internet Message Access Protocol, Version 4 | |
| 161 | SNMP - Simple Network Management Protocol | |
| 443 | HTTPS - Hypertext Transfer Protocol Secure | |
| 2049 | NFS - Network File System |