Network Ports

In computer networking, a port is a communication endpoint. Physical as well as wireless connections are terminated at ports of hardware devices. At the software level, within an operating system, a port is a logical construct that identifies a specific process or a type of network service. Ports are identified for each protocol and address combination by 16-bit unsigned numbers, commonly known as the port number. The most common protocols that use port numbers are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).
A port number is always associated with an IP address of a host and the protocol type of the communication. It completes the destination or origination network address of a message. Specific port numbers are commonly reserved to identify specific services, so that an arriving packet can be easily forwarded to a running application. For this purpose, the lowest numbered 1024 port numbers identify the historically most commonly used services, and are called the well-known port numbers. Higher-numbered ports are available for general use by applications and are known as ephemeral ports.

The Internet Assigned Numbers Authority (IANA) is responsible for the global coordination of the DNS Root, IP addressing, and other Internet protocol resources. This includes the registration of commonly used port numbers for well-known Internet services

The port numbers are divided into three ranges: the well-known ports, the registered ports, and the dynamic or private ports.
The well-known ports (also known as system ports) are those from 0 through 1023. 

Port numberAssignment
20File Transfer Protocol (FTP) Data Transfer
21File Transfer Protocol (FTP) Command Control
22Secure Shell (SSH) Secure Login
23Telnet remote login service, unencrypted text messages
25Simple Mail Transfer Protocol (SMTP) E-mail routing
53Domain Name System (DNS) service
80Hypertext Transfer Protocol (HTTP) used in the World Wide Web
110Post Office Protocol (POP3)
119Network News Transfer Protocol (NNTP)
123Network Time Protocol (NTP)
143Internet Message Access Protocol (IMAP) Management of digital mail
161Simple Network Management Protocol (SNMP)
194Internet Relay Chat (IRC)
443HTTP Secure (HTTPS) HTTP over TLS/SSL

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