Common Port Numbers

Port	Protocol	Service	Description
20, 21	TCP	FTP	File Transfer Protocol
22	TCP	SSH	Secure Shell
23	TCP	Telnet	Telnet remote login service
25	TCP	SMTP	Simple Mail Transfer Protocol
53	TCP/UDP	DNS	Domain Name System
80	TCP	HTTP	HyperText Transfer Protocol
110	TCP	POP3	Post Office Protocol v3
143	TCP	IMAP	Internet Message Access Protocol
443	TCP	HTTPS	HTTP Secure
993	TCP	IMAPS	IMAP over SSL/TLS
995	TCP	POP3S	POP3 over SSL/TLS

Port Ranges

Port Range	Usage	Description
0-1023	Well-known ports	Assigned by IANA for standard services
1024-49151	Registered ports	Assigned by IANA for specific services
49152-65535	Dynamic/Private ports	Available for private use

Port Security Considerations

• Open Ports: Unnecessary open ports increase security risk
• Firewall Rules: Configure firewalls to only allow required ports
• Port Scanning: Regular port scans help identify vulnerabilities
• Default Ports: Change default ports for sensitive services
• Port Forwarding: Only forward ports that are absolutely necessary

IANA Port Assignments

The Internet Assigned Numbers Authority (IANA) maintains the official list of port number assignments. This database is regularly updated and contains:

• Well-known ports (0-1023)
• Registered ports (1024-49151)
• Dynamic ports (49152-65535)

You can find the complete list at: IANA Service Name and Transport Protocol Port Number Registry

TCP vs UDP