# WHATPORT(9100)

## NAME

port 9100 — Raw printing (AppSocket / JetDirect, PDL data stream) — A network printer: send bytes, they print — no protocol, no login.

Protocol: TCP  
IANA registry

## DESCRIPTION

Registered with IANA as pdl-datastream / hp-pdl-datastr, this is the AppSocket protocol, better known as JetDirect after the HP print servers that popularised it. There is no handshake and no authentication: the client opens the socket, writes a page description stream such as PostScript, PCL, or ZPL, and closes it. CUPS drives it with the socket backend (socket://host:9100), and it is one of the most commonly open ports on any office network. Label printers, MFPs, and print server appliances all sit here.

## EXPOSURE

**Do not expose.** Anyone who can reach the port can print, waste consumables, and on many devices push firmware or PJL commands that change settings — there is no authentication in the protocol at all.

## CHECK

```sh
nc -vz -w 3 TARGET 9100
```

## SEE ALSO

- docs — [CUPS — Network printing (AppSocket/JetDirect on port 9100)](https://www.cups.org/doc/network.html) (cups.org)
- iana — [IANA port registry — 9100 (pdl-datastream)](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=9100) (iana.org)

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HTML: <https://whatport.net/9100/> · JSON: <https://whatport.net/9100.json> · full dataset: <https://whatport.net/ports.json>