Port 598: SCO Web Server Manager 3 — A relic from the Unix wars

Port 598 is officially assigned to sco-websrvrmg3 (SCO Web Server Manager 3), a management interface from The Santa Cruz Operation's Unix systems.¹ Both TCP and UDP protocols can use this port, though in practice, you'll rarely encounter traffic here today.

What Was SCO Web Server Manager?

The Santa Cruz Operation (SCO) dominated the x86 Unix market in the 1980s and 1990s. Founded in 1979, SCO sold Unix variants for Intel processors—Xenix, SCO OpenServer, and UnixWare—before the Linux revolution made proprietary Unix systems obsolete.²

SCO OpenServer 5, released in 1995, included web server capabilities and management tools. The Web Server Manager was the administrative interface for configuring and monitoring these web services. Port 598 carried the management traffic between the server and its administrative clients.

This was the era when running a web server meant configuring Unix systems by hand, when Apache was new, when "Internet gateway servers" were a product category. SCO's systems powered early Internet infrastructure, including PizzaNet—Pizza Hut's groundbreaking online ordering system in 1994.³

Why This Port Exists

The well-known port range (0-1023) was assigned by IANA to services that needed consistent port numbers across all Unix systems. Port 598 was registered by Simon Baldwin from SCO to ensure their Web Server Manager would use the same port everywhere it was deployed.

In the mid-1990s, this mattered. System administrators expected services to run on predictable ports. Port 25 was always SMTP. Port 80 was always HTTP. Port 598 was always SCO's web server management interface.

The Reality Today

SCO sold its Unix business to Caldera Systems in 2001.⁴ The company transformed, the products faded, and the infrastructure moved on. Modern web servers use different management approaches—configuration files, REST APIs, web-based control panels. The protocol that once ran on port 598 is essentially extinct.

If you see traffic on port 598 today, you've found either:

• A legacy SCO OpenServer system still running somewhere (they exist, barely)
• A port scan testing every well-known port
• Malware or a misconfigured service squatting on an unused port

Checking What's Listening

To see if anything is listening on port 598 on your system:

Linux/macOS:

sudo lsof -i :598
sudo netstat -tulpn | grep :598

Windows:

netstat -ano | findstr :598

Most systems will return nothing. The port sits empty, reserved for software that no longer runs.

Why Unassigned Ports Matter

Port 598 isn't technically unassigned—it has an official IANA registration. But it's effectively abandoned. These ghost ports matter because they show how the Internet's infrastructure evolves. Services rise, dominate, and disappear. Their port numbers remain in the registry like archaeological artifacts.

The well-known port range is finite—only 1,024 slots. Some are eternal (port 22 for SSH, port 443 for HTTPS). Others, like port 598, are epitaphs for technologies that once mattered.

Every protocol eventually becomes legacy. Every port assignment is a time capsule. Port 598 is where SCO's web management protocol lives now—in the registry, but nowhere else.