- Port
- 23
- Protocol used by the service
- TCP
- IANA registrations
- TCP/UDP
- Encryption
- Unencrypted
- IANA description
- Telnet
- IANA service name
- telnet
Note: IANA has formally registered Telnet on TCP/UDP, but in real-world practice this service operates over TCP only — a formal registration on a transport doesn't guarantee the protocol is actually implemented or used over it. This page's Protocol field reflects genuine usage, not just the registry entry.
What port 23 is used for
Legacy remote terminal access. Largely obsolete for general use, but still found on some older network equipment and embedded/industrial devices.
Is port 23 encrypted?
Not encrypted at all — credentials and all session data are sent in plaintext, readable by anyone able to observe the traffic.
Firewall & exposure considerations
Should not be exposed to the open internet under any normal circumstance. If legacy equipment genuinely requires it, restrict access to an isolated management network, never a public-facing interface.
Related ports
References
Look up any other port
Search the full IANA registry — all 6,100+ ports and 12,500+ protocol-specific records — on the Port Lookup tool.
Last reviewed: . Data source: IANA Service Name and Transport Protocol Port Number Registry. Security and usage notes are this site's own editorial content, not official IANA data.