Introduction: The Standardized Entrance

While there are over 65,000 ports available, about a dozen of them do 99% of the work on the internet. These are called **Well-Known Ports**. Every computer in the world agrees that specific numbers belong to specific tasks. This agreement is what allows a browser in Tokyo to talk to a server in London without any confusion.

In this guide, we'll list the most common ports and explain exactly what travels through each one.

The Web & Remote Access

Port 80 (HTTP): Used for standard, unencrypted web browsing.
Port 443 (HTTPS): Used for secure, encrypted web browsing. If you see a padlock in your browser, you are using Port 443.
Port 22 (SSH): The 'Secure Shell'. This is the standard way for administrators to remotely log into and control servers.

Email & Files

Port 25 (SMTP): Used for sending emails.
Port 110 (POP3) / 143 (IMAP): Used for receiving emails into your inbox.
Port 21 (FTP): The 'File Transfer Protocol'. An old but still common way to move files between computers.

Diagnostics & Games

Port 53 (DNS): The port that handles all the 'naming' lookups for the web.
Port 3389 (RDP): Used for Windows Remote Desktop connections.

Conclusion

Understanding these ports is the first step toward securing your network. A good rule of thumb? If you don't need a port, close it! See which of these ports are open on your IP here.