Port 92: NPP — The Internet's First Attempt at Printing

Port 92 is assigned to the Network Printing Protocol (NPP), an early attempt by the IETF to standardize how computers send documents to printers over a network. If you have ever cursed at a printer, this port is part of the origin story.

What NPP Was Supposed to Do

In 1990, the IETF chartered the Network Printing Protocol working group to solve what seemed like a straightforward problem: let any computer on the Internet print to any printer on the Internet.¹

At the time, network printing existed, but it was a mess. Every Unix variant had its own line printer daemon. Every vendor had proprietary extensions. If your computer and your printer happened to speak the same dialect, you could print. If they didn't, you couldn't. There was no standard, just accumulated convention.

The NPP working group set out to fix this. Port 92 was registered for the protocol by Louis Mamakos,² a network engineer at the University of Maryland who had helped build the reference implementation of OSPF³ and would later become CTO of Vonage.

What Actually Happened

The working group's most significant output was RFC 1179, published in August 1990.⁴ But RFC 1179 didn't define a new protocol. It documented the existing Line Printer Daemon (LPD) protocol that was already running on port 515 across Unix systems worldwide. The RFC was explicit: this was informational only, not a standard. The working group was describing what existed, not prescribing what should exist.

The group's other objectives, designing a proper Internet-scale printing protocol, proved harder than expected. The working group concluded without producing a new standard for port 92.

The Long Road to Actual Network Printing

In 1991, printer and network manufacturers formed the Network Printing Alliance, which reorganized in 1993 as the Printer Working Group (PWG).⁵ In 1996, Novell proposed creating a proper Internet printing protocol. The IETF chartered the Internet Printing Protocol (IPP) working group in March 1997.

IPP succeeded where NPP stalled. It defined a real protocol using HTTP as its transport, running on port 631. IPP/1.1 was published as RFCs 8010 and 8011 and became Internet Standard 92 (STD 92) in June 2018.⁶

That number, STD 92, matching the port number where the first attempt was registered, is a coincidence. But it feels like a footnote the Internet wrote for itself.

The Port Today

Port 92 sees almost no traffic in modern networks. LPD runs on port 515. IPP runs on port 631. The protocol that was supposed to claim port 92 never materialized into something that shipped.

You are unlikely to find anything listening on port 92. If you do, investigate:

# Check if anything is listening on port 92
sudo lsof -i :92

# Scan port 92 on a specific host
nmap -p 92 <host>

# Check for active connections on port 92
sudo netstat -tlnp | grep ':92 '

Security Considerations

Because port 92 is in the well-known range (0 to 1023), binding to it requires elevated privileges on most operating systems. This provides a baseline layer of protection since unprivileged processes cannot claim it.

Port 92 does not appear on major Trojan port lists. However, any open port with no legitimate service running is a potential vector. If you find port 92 open and cannot identify the process, treat it as suspicious.

The Story This Port Tells

Port 92 is a reservation for a protocol that never fully arrived. The problem it was meant to solve, network printing, turned out to be one of the most stubbornly difficult challenges in computing. Not because sending bytes to a printer is hard, but because printers are complicated machines with complicated state, and describing "print this document the way I want it" across a network requires agreeing on paper sizes, color profiles, duplex modes, job queues, error recovery, authentication, and a dozen other things that seemed simple until you tried to standardize them.

The IETF tried once with NPP on port 92. They tried again with IPP on port 631. The second time worked. But the first attempt is still here in the registry, a port number holding a place for a protocol that taught the Internet how hard printing really is.