The well-known ports are those from 0 through 1023. Examples include:
- 21: File Transfer Protocol (FTP)
- 22: Secure Shell (SSH)
- 23: Telnet remote login service
- 25: Simple Mail Transfer Protocol (SMTP)
- 53: Domain Name System service
- 80: Hypertext Transfer Protocol (HTTP) used in the World Wide Web
- 110: Post Office Protocol
- 119: Network News Transfer Protocol (NNTP)
- 161: Simple Network Management Protocol (SNMP)
- 443: HTTPs with Transport Layer Security or Secure Sockets Layer
