# WHATPORT(2121)

## NAME

port 2121 — Alternate FTP / FTP proxy — FTP's unprivileged twin — where an FTP server or FTP proxy lands when it cannot bind port 21.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA registers 2121 as SCIENTIA-SSDB, but that is not what runs there. In practice 2121 is the conventional alternate FTP port: it is above 1024, so a daemon can bind it without root, and it is where FTP proxies land — Nmap names the port ccproxy-ftp after CCProxy's FTP proxy service. It is common enough to matter, open on roughly 0.6% of scanned hosts, well ahead of everything around it. A connection returns a normal FTP banner, and the protocol is RFC 959 FTP with all of its properties intact.

## EXPOSURE

**Expose with care.** Same rules as port 21: cleartext credentials unless the session negotiates AUTH TLS (RFC 4217), and an open FTP proxy here can be abused to relay traffic. Moving FTP off 21 hides it from nobody.

## CHECK

```sh
printf 'QUIT\r\n' | nc -v TARGET 2121
```

## SEE ALSO

- spec — [RFC 959 — File Transfer Protocol (FTP)](https://www.rfc-editor.org/rfc/rfc959.html) (rfc-editor.org)
- source — [nmap-services — 2121/tcp listed as ccproxy-ftp](https://github.com/nmap/nmap/blob/master/nmap-services) (github.com)
- 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)

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HTML: <https://whatport.net/2121/> · JSON: <https://whatport.net/2121.json> · full dataset: <https://whatport.net/ports.json>