Port 2291 is a registered port, assigned by IANA to SEIKO EPSON Corporation in June 2006 for the EPSON Advanced Printer Share Protocol (service name: eapsp). It operates on both TCP and UDP.1
You've probably never thought about it. That's the point.
What It Does
When an Epson printer sits on a network and multiple computers share access to it, something has to coordinate that. The EPSON Advanced Printer Share Protocol handles discovery and communication between Epson's networking software and its printers on a local network.
Port 2291 is part of how Epson's software stack — including EpsonNet Print and related utilities — finds printers on the network, manages shared access, and keeps jobs flowing. It runs alongside other well-known printer ports like 9100 (raw print data) and 631 (IPP), but handles Epson-specific coordination that the standard protocols don't cover.
The Registered Port Range
Port 2291 sits in the registered port range: 1024 through 49151.
This range is where companies and developers go when they need a stable, official port number for their software. They submit a request to IANA, which reviews and assigns it. The registration gives them a reserved number that other applications should avoid — a way of saying "this is ours."
The range contains over 48,000 ports. Many are claimed by major protocols you know well (HTTP at 80, HTTPS at 443, SSH at 22 are below this range, but MySQL at 3306, PostgreSQL at 5432, and Redis at 6379 live here). Many more are held by vendor protocols like this one — quietly doing their job on networks that need them, invisible to everyone else.
Who Encounters This Port
Mostly, network administrators. Port 2291 shows up in firewall logs when Epson printers are on the network and Epson's printer management software is running. If you're blocking it, print sharing features on Epson network printers may stop working. If you're seeing unexpected traffic on 2291, an Epson device or Epson software is almost certainly the source.
It's not a port that attackers target specifically — it carries no credentials, no sensitive data worth stealing. The security concern, if any, is what it always is with vendor protocols: a proprietary protocol from 2006 running on a printer that hasn't been updated in years. Printers as a category have a troubled security history, and any open port is a potential surface.
How to Check What's Listening
If you want to know whether anything is using port 2291 on your machine:
macOS / Linux:
Windows (Command Prompt, run as administrator):
To check a remote host:
If something is listening on 2291 and you don't have Epson printers or Epson software on your network, it's worth investigating. Unexpected listeners on registered ports can indicate software you forgot you installed — or software you didn't install at all.
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