Port 779 is officially unassigned by IANA, but it has a history. On many Unix systems, you'll find it listed as moira_ureg—Moira user registration—a UDP service from an era when MIT was building the future of campus computing.
What Moira Was
Moira was the service management system for MIT's Project Athena, a joint effort by MIT, Digital Equipment Corporation, and IBM that ran from 1983 to 1991.1 The goal was ambitious: create a campus-wide distributed computing environment where thousands of students could sit down at any workstation and have their entire digital identity available.
Moira managed everything. Mailing lists. User accounts. NFS directories. Post office allocations. DNS records. Print queues. All synchronized across hundreds of servers through a central database and automated updates.2
Port 779 handled one specific piece: user registration.
How User Registration Worked
A student would sit down at an Athena workstation and type userreg as their login name. The registration program would validate their identity, then ask them to choose a real login name and password.
Behind the scenes, the userreg program connected to the Moira registration server on UDP port 779. That single connection triggered a cascade: the server registered the login name in the Moira database, reserved it with Kerberos, allocated an NFS home directory, and configured a post office.3
One UDP packet. Entire digital identity created.
The service was called sms_ureg in early documentation (SMS stood for "Service Management System," Moira's original name) and later moira_ureg after the system was renamed.4
Why Port 779 Matters (And Doesn't)
Moira user registration on port 779 represents a specific moment in computing history—when universities were solving distributed identity management problems that the broader industry wouldn't tackle for another decade.
Today, you won't find anything listening on port 779. Moira itself evolved into other systems. MIT still uses descendants of Moira's architecture, but the original registration protocol is long retired.5
Yet port 779 remains in /etc/services files across Unix systems—a fossil from when MIT was inventing campus computing.
What Port 779 Is Now
Officially, IANA lists port 779 as unassigned. No modern service uses it. If you see traffic on port 779, it's either:
- A legacy system still running ancient Athena software
- Something using an unassigned port for custom services
- Malicious traffic hoping you're not monitoring high-numbered well-known ports
To check what's listening on port 779 on your system:
You'll almost certainly find nothing. Port 779's job is done.
The Historical Context
Project Athena ran from 1983 to 1991 and fundamentally shaped how universities—and eventually companies—think about networked computing.6 Kerberos authentication came from Athena. The X Window System came from Athena. Zephyr instant messaging came from Athena.
And Moira, running on ports like 779, made it all manageable.
The problems Moira solved in the 1980s—centralized user management, automated service provisioning, distributed authentication—are the same problems Active Directory and LDAP solve today. MIT just got there first.
Port 779 is where students became users. Where identity became distributed. Where campus computing became possible.
Why Unassigned Ports Matter
Port 779 shows why even "unassigned" ports have stories. The well-known port range (0-1023) was designed to be managed by IANA, with each port officially assigned to a specific service. But in practice, many ports were claimed by convention—services used them, systems documented them, and they became "semi-official" even without formal IANA assignment.
Some of these informal assignments, like port 779, eventually faded away when the services died. Others became official after years of de facto use. And some remain in limbo—not officially assigned, but not truly empty either.
The port number space is as much archaeology as architecture.
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