Essential Ports and Services
Essential Network Ports and Services
Section titled “Essential Network Ports and Services”What is a port? A port is a logical communication endpoint within an operating system. It allows computers to differentiate between different types of network traffic arriving over the same network interface.
Core Ports and Protocols Reference Table
Section titled “Core Ports and Protocols Reference Table”Below is a detailed list of the most critical network ports you need to know:
| Port | Protocol | Service Name | Description |
|---|---|---|---|
| 20, 21 | TCP | FTP (File Transfer Protocol) | Transfers files between a client and a server. Port 20 is used for data transfer, and port 21 is used for connection control/commands. |
| 22 | TCP | SSH (Secure Shell) | Provides an encrypted and secure channel for remote console login and command execution. It is the standard for managing Linux servers securely. |
| 23 | TCP | Telnet | Provides unencrypted remote console access. It is considered highly insecure because credentials and data travel in cleartext. |
| 25 | TCP | SMTP (Simple Mail Transfer Protocol) | The standard protocol used for routing and sending (pushing) email messages between mail servers (MTAs). |
| 53 | TCP / UDP | DNS (Domain Name System) | Translates human-readable domain names (like google.com) into their corresponding numerical IP addresses. |
| 67, 68 | UDP | DHCP (Dynamic Host Configuration Protocol) | Automatically assigns IP addresses, default gateways, and DNS settings to client devices. Port 67 listens on the server; 68 listens on the client. |
| 80 | TCP | HTTP (Hypertext Transfer Protocol) | Transmits web page data in cleartext (unencrypted) across the internet. |
| 110 | TCP | POP3 (Post Office Protocol v3) | Retrieves (pulls) email from a remote server to a local client. Traditionally downloads the email and deletes it from the server. |
| 143 | TCP | IMAP (Internet Message Access Protocol) | Retrieves email while maintaining a synced connection with the server, allowing simultaneous access from multiple devices. |
| 443 | TCP | HTTPS (Hypertext Transfer Protocol Secure) | Transmits encrypted web traffic using SSL/TLS certificates, ensuring data privacy and integrity. |
| 445 | TCP | SMB (Server Message Block) | Primarily used in Windows environments for file sharing, printer sharing, and accessing remote network resources. |
| 3389 | TCP / UDP | RDP (Remote Desktop Protocol) | Microsoft’s proprietary protocol designed to provide a graphical user interface when connecting to another computer over the network. |