Common Port Numbers
- 20 & 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
- 69: TFTP (Trivial File Transfer Protocol)
- 80: Hypertext Transfer Protocol (HTTP) used in the World Wide Web
- 109: Post Office Protocol (POP2)
- 110: Post Office Protocol (POP3)
- 119: Network News Transfer Protocol (NNTP)
- 143: Internet Message Access Protocol (IMAP)
- 161: Simple Network Management Protocol (SNMP)
- 389 LDAP (Lightweight Directory Access Protocol)
- 443: HTTP Secure (HTTPS)
- 546: DHCP - Client
- 547: DHCP - Server
