What is a network port?

The physical port on your laptop lets you communicate with peripheral devices such as a keyboard and mouse to connect with internet devices via Ethernet cables.

A port is a location on the recipient computer where data is received. In simple terms, if a software application needs to communicate with each other, 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 knows ports also known as system ports are numbered 0 to 1023. For example, the SSH port which uses port 22.

ssh teslimodumuyiwa@gmail.com -v

debug1: Connecting to gmail.com [216.58.223.197] port 22.

From the text above SSH is trying to connect to gmail.com using port 22. You can use -p to specify the port you will like to use but by default, SSH will use port 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: