Port 85: MIT ML Device — A Ghost in the Machine

Port 85 is assigned to MIT ML Device (mit-ml-dev), a service associated with a specific computer at the MIT AI Lab. That computer, a DEC PDP-10 KA10 with serial number 198, was known as "ML" for Mathlab.¹ It ran from 1971 to 1984. The port assignment outlived the machine by decades.

What MIT ML Device Was

In the 1970s, MIT's AI Lab and Laboratory for Computer Science operated several PDP-10 computers, each with a name: AI, DM, MC, and ML.² The ML machine ran the Incompatible Timesharing System (ITS), a deliberately contrarian operating system built by hackers who rejected the constraints of MIT's official Compatible Time-Sharing System.

ML's primary purpose was running Macsyma, one of the first computer algebra systems.³ Researchers used it for symbolic mathematics, the kind of computation where you ask a computer to simplify an integral rather than just crunch numbers.

Port 85 (along with port 83) was registered to provide device-level network access to the ML machine. The contact listed in the IANA registry is David Reed.⁴

The David Reed Connection

The name on this port assignment belongs to David P. Reed, who would go on to design the User Datagram Protocol (UDP) and co-author one of the most influential papers in computer science: "End-to-End Arguments in System Design" with Jerome Saltzer and David Clark.⁵ That paper articulated the principle that intelligence belongs at the edges of a network, not in the middle. It shaped the architecture of the Internet itself.

Port 85 is from before all of that. It is a small administrative entry from Reed's time at MIT, a port reservation for a machine that helped create the environment where those larger ideas could form.

The Port Today

The ML machine was decommissioned in 1984. No modern software implements the MIT ML Device protocol. But the port number remains assigned in the IANA registry, because port assignments are rarely reclaimed.

In practice, port 85 occasionally appears in the wild as an alternative HTTP port for DVR and IP camera web interfaces. Devices built on Xiongmai (XMeye) firmware sometimes run their embedded web administration panel on port 85 instead of the standard port 80.⁶ If you see port 85 open on a network scan, it is almost certainly one of these devices, not a PDP-10.

Port Range Context

Port 85 falls within the well-known port range (0 through 1023). These ports are reserved by IANA and historically required superuser privileges to bind on Unix systems.⁷ The well-known range contains the Internet's most critical services: HTTP on 80, HTTPS on 443, SSH on 22, DNS on 53.

It also contains dozens of assignments like port 85: services that were real and necessary in the 1970s and 1980s, assigned to specific machines at specific universities, now silent. The IANA registry is an archaeological record. Every entry tells you something about what mattered at a particular moment in computing history.

How to Check What Is Listening on Port 85

On macOS or Linux:

# Check if anything is listening on port 85
sudo lsof -i :85

# Scan port 85 on a remote host
nmap -p 85 <hostname>

On Windows:

# Check local listeners on port 85
netstat -an | findstr :85

If you find port 85 open on your network and you did not intentionally configure it, investigate. It may be an IP camera or DVR with a web interface exposed, potentially with default credentials.

Why Unassigned and Legacy Ports Matter

The 65,535 ports available to TCP and UDP are a finite resource. The well-known range is the most constrained: only 1,024 slots for the protocols that define how the Internet works. Many of those slots hold assignments from the 1970s and 1980s for services that no longer exist.

These legacy assignments are not waste. They are a record. Port 85 tells you that in the early 1970s, a computer named ML at MIT was important enough to get two port numbers. That machine helped develop Macsyma, trained a generation of hackers, and sat in the same building where the ideas behind UDP, Chaosnet, and the end-to-end principle were taking shape.⁸

The port is quiet now. The machine it pointed to has been gone for forty years. But the number remains in the registry, holding its place, a small monument to a KA10 that earned its name.