# WHATPORT(5998)

## NAME

port 5998 — Unassigned (historically NCD X terminal diagnostics) — Unassigned by IANA; historically the diagnostic telnet port of Network Computing Devices X terminals.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA lists 5995-5998 as Unassigned, so there is no current owner. The name that persists in scanner databases is `ncd-diag` — nmap still labels 5997/5998/5999 as the preferences, diagnostic and configuration telnet ports of Network Computing Devices X terminals, thin clients from the late 1980s and 1990s. That hardware is long gone, so a listener today is an unrelated application that picked a free port just below 6000.

## EXPOSURE

**Expose with care.** No registered service means the port number tells you nothing — identify the process locally before allowing any access. If it genuinely is a telnet-style diagnostic console, treat it as never.

## CHECK

```sh
nmap -Pn -sV -p 5998 TARGET
```

## SEE ALSO

- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)
- source — [nmap-services — the port-frequency database](https://github.com/nmap/nmap/blob/master/nmap-services) (github.com)

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HTML: <https://whatport.net/5998/> · JSON: <https://whatport.net/5998.json> · full dataset: <https://whatport.net/ports.json>