Ports. Everybody needs a port. Sometimes.

Ports. Everybody needs a port. Sometimes. Today we are going to talk about ports. As used by TCP and UDP. Except, I am not going to mention TCP and UDP from now. In fact I’m not to talk about the technical details of ports – or what a port is, either. Today I look into port ranges and a bit into standards.

Port ranges

You probably know that there are 65535 TCP Ports and another 65535 UDP ports, and that this range is further divided into three separate ranges. These ranges are the well-known ports, the registered ports, and the dynamic or private ports.

The well-known ports

The well known ports are those in the 0 – 1023 range. Examples includes:

• 21: File Transfer Protocol (FTP)
• 22: Secure Shell (SSH)
• 23: Telnet remote login service
• 25: Simple Mail Transfer Protocol (SMTP)
• 53: Domain Name System (DNS) service