| Port | Protocol | Description |
|---|---|---|
| TCP 20 & 21 | FTP | File Transfer Protocol for file transfer. |
| UDP 21 | Not used | No common file transfer protocol uses UDP 21. |
| TCP 22 | SSH | Secure Shell, used for secure remote login. SFTP operates over SSH. |
| TCP 23 | Telnet | Used for unencrypted text communications and remote logins. |
| TCP 515 | LPD | Line Printer Daemon, used for printing services. |
| TCP 25 | SMTP | Simple Mail Transfer Protocol, used for email transmission. |
| TCP 53 | DNS | Domain Name System, used for resolving domain names to IP addresses. |
| TCP 110 | POP3 | Post Office Protocol 3, used for retrieving emails. |
| TCP 80 | HTTP | Hypertext Transfer Protocol, used for web traffic (no confidentiality). |
| TCP 143 | IMAP | Internet Message Access Protocol, used for retrieving emails. |
| TCP 389 | LDAP | Lightweight Directory Access Protocol, unsecure. |
| TCP 636 | LDAPS | LDAP over SSL/TLS, secure version of LDAP. |
| TCP 9100 | Network Printers | Used for direct IP printing. |
| UDP 69 | TFTP | Trivial File Transfer Protocol, a simplified version of FTP. |
| 6000-6063 | X Windows, Linux | Ports used by X Windows system for GUI services. |
| TCP 443 | HTTPS | Hypertext Transfer Protocol Secure, used for secure web traffic. |
| TCP 445 | SMB/Active Directory | Used by Server Message Block protocol and Active Directory. |
| TCP 1433 | Microsoft SQL | Default port for Microsoft SQL Server database. |
| TCP 1521 | Oracle Database | Default port for Oracle Database. |
| TCP 3389 | RDP | Remote Desktop Protocol, used for remote desktop connections. |
| TCP 3268/3269 | Global Catalog | Used for querying the Global Catalog in Active Directory (unsecure/secure). |
| TCP/UDP 137-139 | NetBIOS | Used for NetBIOS services, including name resolution and file sharing. |
This table summarizes key TCP and UDP ports, their associated protocols, and their primary functions. Understanding these ports is crucial for network security, troubleshooting, and configuration.