# WHATPORT(543)

## NAME

port 543 — klogin (Kerberized rlogin) — Kerberized rlogin — the r-services with Kerberos tickets instead of .rhosts trust.

Protocol: TCP  
IANA registry

## DESCRIPTION

TCP 543 is registered as "klogin": rlogin authenticated with Kerberos, so the client presents a ticket rather than relying on host-based .rhosts files, and the session can optionally be encrypted. It was part of the Kerberos-patched application suite that shipped with MIT krb5 and with commercial Unix. MIT split those applications out of the core krb5 distribution in release 1.8 to be maintained separately, and SSH with GSSAPI has taken over the job, so a listener on 543 today means a very old Kerberos realm or an appliance that never updated.

## EXPOSURE

**Do not expose.** An unmaintained interactive login service; even when the Kerberos authentication holds, the deployment around it is a decade or more past support. Use SSH.

## CHECK

```sh
nc -vz -w 3 TARGET 543
```

## SEE ALSO

- docs — [MIT Kerberos 5 Release 1.8 release notes ("Remove applications to a separate distribution")](https://web.mit.edu/Kerberos/krb5-1.8/README-1.8.txt) (web.mit.edu)
- iana — [IANA Service Name and Transport Protocol Port Number Registry — 543](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=543) (iana.org)

---

HTML: <https://whatport.net/543/> · JSON: <https://whatport.net/543.json> · full dataset: <https://whatport.net/ports.json>