What This Port Was For
Port 616 is officially assigned to sco-sysmgr—the SCO System Administration Server.1 It operates on both TCP and UDP protocols and was designed for remote system administration of SCO Unix systems.
SCO (Santa Cruz Operation) built Unix operating systems for Intel processors in the 1980s and 1990s. During that era, when graphical interfaces were replacing command-line administration, SCO created tools to manage their Unix systems remotely. Port 616 was how administrators connected to those management servers.2
The Company That No Longer Exists
The Santa Cruz Operation was founded in 1979 and became a leader in bringing Unix to Intel-based computers.3 They produced SCO Xenix (a port of Microsoft Xenix) in the 1980s, then SCO Unix, SCO OpenServer, and SCO Open Desktop through the 1990s.
By the early 1990s, SCO Unix was a significant player in the server market. Version 4.0, announced in 1992, introduced enhanced administration tools including the "sysadmsh" shell and mouse-driven interfaces.4 The sco-sysmgr service on port 616 was part of this administrative infrastructure—it let you manage Unix systems without memorizing arcane commands.
But SCO Unix lost the server wars to Linux and other Unix variants. The company went through mergers, lawsuits, and bankruptcy. The operating system is effectively extinct. Nobody deploys new SCO Unix systems in 2026.
What You'll Find on Port 616 Today
Almost certainly nothing.
If you scan modern networks for port 616, you're unlikely to find anything listening. The service it was designed for doesn't exist anymore. Legacy SCO Unix installations that might still run somewhere—in industrial control systems or ancient infrastructure nobody wants to touch—are rare enough to be legends.
The port assignment remains in the IANA registry because port assignments are permanent. Once assigned, they stay assigned, even after the software dies and the company disappears.
Why Obsolete Ports Matter
Port 616 is a monument. It marks a moment in computing history when Unix ran on Intel, when remote administration required dedicated protocols, when SCO was a name that mattered.
The IANA registry is full of these monuments—ports assigned to protocols that nobody uses, services that nobody runs, companies that no longer exist. They're not useless. They're context. They show what mattered enough to deserve a port number. They show what changed.
Port 616 reminds us that the infrastructure we depend on today will someday be obsolete. The protocols we think are permanent will be replaced. The companies we think are essential will disappear. The port assignments will remain, waiting for connections that will never come.
Checking What's Listening
If you want to see if anything is actually using port 616 on your system:
Linux/Mac:
Windows:
If something is listening and it's not a decades-old SCO Unix system, you should investigate. Modern software shouldn't be using this port.
The Well-Known Range
Port 616 falls in the well-known ports range (0-1023), which means it was assigned by IANA for a specific service. These ports require root/administrator privileges to bind to on Unix-like systems—a security measure from an era when multi-user systems needed to prevent normal users from impersonating system services.
The irony is that the service this port was assigned to protect is gone. The privilege requirement remains.
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