Port 360: scoi2odialog — A Ghost From the Unix Wars

Port 360 sits in the well-known ports range with an official assignment, but almost nobody uses it anymore. It's assigned to scoi2odialog, a protocol that carried messages between intelligent I/O processors on SCO OpenServer systems during the 1990s.

This is what happens when technology moves on but port assignments remain.

What scoi2odialog Was

The name breaks down like this: SCO I2O Dialog.

• SCO: The Santa Cruz Operation, a company that sold Unix systems in the 1980s and 1990s
• I2O: Intelligent Input/Output, a specification from the 1990s that used special processors to handle I/O operations
• Dialog: The communication protocol between these processors

I2O was supposed to eliminate I/O bottlenecks by offloading device management to dedicated processors.¹ Multiple independent processors would send messages back and forth, coordinating storage, network interfaces, and other devices without bothering the main CPU.

SCO OpenServer supported I2O starting with UnixWare System V Release 5 in the late 1990s.² Port 360 was assigned to Keith Petley for the I2O dialog protocol that these systems used.³

The Unix Wars Context

Understanding port 360 requires understanding what was happening to Unix in the 1990s.

SCO was one of many companies selling Unix systems when the operating system market fractured into competing versions. Sun had Solaris. IBM had AIX. HP had HP-UX. SCO had OpenServer and UnixWare. Everyone was fighting for enterprise customers.

Then Linux arrived and offered Unix-like functionality for free.

SCO fought back with lawsuits instead of innovation. They sued IBM, claiming Linux contained SCO's intellectual property. They sued Novell over Unix ownership. They sued AutoZone for using Linux. The company spent years in court while their products became irrelevant.

Port 360 is a artifact from that era—infrastructure for systems that lost the war.

What This Port Represents

Port 360 is in the well-known ports range (0-1023), which means it was assigned by IANA through formal procedures. Getting a well-known port required IETF Review or IESG Approval, demonstrating that scoi2odialog was considered important infrastructure at the time.⁴

The port is assigned for both TCP and UDP, suggesting the protocol needed both reliable connections and potentially lower-latency datagram communication for I/O operations.

Today, you won't find scoi2odialog traffic on modern networks. SCO OpenServer installations are rare. The I2O specification itself is obsolete, replaced by more efficient architectures. But the port assignment remains in the official registry, a placeholder for a protocol that the Internet has mostly forgotten.

Security Note

Because port 360 is rarely used for legitimate purposes anymore, security scanners have historically flagged it as potentially suspicious. Some malware has used uncommon ports like 360 for command and control, but this has nothing to do with the original scoi2odialog protocol.⁵

If you see port 360 open on a modern system, investigate what's listening. It's probably not SCO OpenServer.

How to Check This Port

On Linux or macOS:

# See if anything is listening on port 360
sudo lsof -i :360

# Check for connections
netstat -an | grep 360

On Windows:

# See what's using port 360
netstat -ano | findstr :360

You'll almost certainly find nothing. This is a ghost port.

Related Ports

Port 360 exists in a neighborhood of early Unix and network management protocols:

• Port 359: Previously assigned, de-assigned in November 2023⁴
• Port 361-370: Various other early protocol assignments from the same era

Why This Port Matters

Port 360 reminds us that the Internet has a memory. The port registry preserves assignments for protocols that barely anyone uses anymore, maintaining namespace stability even as the software landscape changes completely.

Somewhere in a data center, there might still be a SCO OpenServer machine with port 360 open, faithfully waiting for I2O messages that will never arrive. The Unix wars are over. Linux won. But the ports that the losers used remain in the registry, monuments to battles most people have forgotten.

The Internet is built on layers of extinct protocols, deprecated systems, and abandoned standards. Port 360 is one small piece of that archaeological record.