A port is a communication point where one or more computers in a network talk with each other through a program or software. There are about 0-65535 ports assigned to do specific tasks in a PC. Most ports operate with TCP or UDP protocol.

Port numbers are officialy assigned by an organisation called IANA and ports are allocated to various needs to avoid confusion.

Port Types & Classification

Ports are classified into 3 main categories..

  • Well Known Ports (Port numbers 0 — 1023)
  • Registered Ports (Port numbers1024 — 49151)
  • Private or Dynamic Ports (Port numbers 49152 — 65535)

Well Known Ports
Well known ports are used by system or processes run by root or with specific previleges. The port numbers range from 0 to 1023.

Registered Ports
The registered port numbers range from 1024-49151. Such ports are used by programs run by users in the system.

Private/Dynamic Ports
Private ports are not assigned for any specific purpose. its range are from range 49152?65535

Difference TCP vs UDP Protocol

TCP/IP Protocol
UDP Protocol
It is a connection oriented protocol It is connectionless protocol which means it can send packets without establishing connection with the receiver at first.
It has flow control and error correction It is error prone during transmission.
It is not fast and primarily used for data transmission like (http,ssh,smtp,ftp, mail etc.) It is fast and used mostly for audio and video streaming.
Most common services requiring confirmation of delivery like http,ssh,smtp,ftp, mail etc. use TCP ports UDP ports are commonly used by services or programs that dont require the confirmation of delivery of packets. Most commonly used is DNS queries using UDP port 53.


Commonly Used Port Numbers

The following port numbers are unofficial list of commonly used for linux/unix based servers.

Port Number Protocol
21 TCP FTP (File Transfer Protocol)
22 TCP/UDP SSH (ssh,scp copy or sftp)
23 TCP/UDP Telnet
25 TCP/UDP SMTP (for sending outgoing emails)
43 TCP WHOIS function
53 TCP/UDP DNS Server (Domain name service for DNS requests)
DHCP Server
DHCP Client
70 TCP Gopher Protocol
79 TCP Finger protocol
110 TCP POP3 (for receiving email)
119 TCP NNTP (Network News Transfer Protocol)
143 TCP/UDP IMAP4 Protocol (for email service)
389 TCP/UDP LDAP (light weight directory access)
443 TCP Secure HTTP over SSL (https)
465 TCP Secure SMTP (email) using SSL
990 TCP/UDP Secure FTP using SSL
993 TCP Secure IMAP protocol over SSL (for emails)
1433 TCP/UDP Microsoft SQL server port
2082 TCP Cpanel default port
2083 TCP Cpanel over SSL
2086 TCP Cpanel Webhost Manager (default)
2087 TCP Cpanel Webhost Manager (with https)
2095 TCP Cpanel Webmail
2096 TCP Cpanel secure webmail over SSL
2222 TCP DirectAdmin Server Control Panel
3306 TCP/UDP MySQL Database Server
4643 TCP Virtuosso Power Panel
5432 TCP PostgreSQL Database Server
8080 TCP HTTP port (alternative one for port 80)
8087 TCP Plesk Control Panel Port (default)
8443 TCP Plesk Server Control Panel over SSL
9999 TCP Urchin Web Analytics
10000 TCP Webmin Server Control Panel
19638 TCP Ensim Server Control Panel

More unofficial list of ports and assignments s available here
Official ports and its assignments are published at the IANA website.

Note: The above published ones are unofficial list compiled from various sources.