14 common network ports you should know

The physical ports on your computer allow communicate with peripheral devices such as your keyboard and mouse and to connect with internet devices via Ethernet cables.

Witin computer networking, ports serve a similar purpose. When a computer system seeks to connect to another computer, the port serves as a communication endpoint. It is also possible for different services running on the same computer to expose various ports and communicate with one another using these ports. In simple terms, if a software application or service needs to communicate with others, it will expose a port. Ports are identified with positive 16-bit unsigned integers, ranging from 0 to 65535. Other services use this port number to communicate with the service or app. Port numbers are divided into three ranges: well-known ports, registered ports, and dynamic or private ports.

Well-known ports (also known as system ports) are numbered from 0 through 1023. For example, to connect to the host example.com via SSH, I would use this command:

ssh [email protected] -v

In this example, -v stands for verbose, and you should see output similar to this:

debug1: Connecting to example.com [<IP Addr>] port 22

As shown, SSH is trying to connect to example.com using port number 22. You may use the -p option to specify another port number; otherwise, SSH will default to 22.

The Internet Assigned Numbers Authority (IANA) has assigned port numbers to commonly used services like SSH, FTP, HTTP, HTTPS, and others. Here are some of the most common ones:

Port Number

Usage

File Transfer Protocol (FTP) Data Transfer

File Transfer Protocol (FTP) Command Control

Secure Shell (SSH)

Telnet – Remote login service, unencrypted text messages

Simple Mail Transfer Protocol (SMTP) E-mail Routing

Domain Name System (DNS) service

Hypertext Transfer Protocol (HTTP) used in World Wide Web

110

Post Office Protocol (POP3) used by e-mail clients to retrieve e-mail from a server

119