Port 216: CAIlic — The License Enforcer

Port 216 is assigned to CAIlic, Computer Associates International License Server. This port handled the communication between CA's software products and their central licensing system—the infrastructure that determined whether your expensive enterprise software would start or display a licensing error.¹

What CAIlic Did

CAIlic was Computer Associates' network license management system. When CA software started, it would connect to port 216 (both TCP and UDP) to verify that your organization had valid licenses. The license server would check:

• How many licenses you purchased
• How many were currently in use
• Whether your maintenance contract was current
• Whether the software was authorized to run

If everything checked out, the software ran. If not, it refused to start. This was enterprise software licensing enforcement in action.

The Computer Associates Empire

Computer Associates was founded in 1976 by Charles Wang and Russell Artzt, initially focusing on mainframe utility software.² The company grew explosively through aggressive acquisitions—over 60 by the mid-1990s—buying up enterprise software companies across disparate fields: system monitoring, ID management, security, anti-virus.³

By the 1990s, CA had become one of the world's largest independent software companies. They had customers who needed their software with few alternatives, and they enforced their licensing aggressively. Their legal staff maintained that no CA product could be transferred after a box was opened, despite language in their own license agreements that permitted it.⁴

Port 216 was the technical mechanism that made this enforcement possible across corporate networks.

How License Servers Work

Network license servers solve a specific enterprise problem: you buy 50 licenses for software but have 200 employees. Instead of installing licenses on individual machines, you run a central license server. When someone launches the software:

1. The application connects to port 216 on the license server
2. The server checks if a license is available
3. If yes, it grants a temporary lease
4. When the user closes the software, the license returns to the pool

This let companies manage licenses centrally and ensure compliance. It also meant that if the license server went down, nobody's software worked.

The End of Computer Associates

In July 2018, Broadcom Inc. acquired CA Technologies (as Computer Associates had renamed itself) for $18.9 billion in cash—the largest sale of an enterprise software company on record.⁵ The acquisition puzzled many observers because the two companies' businesses had little in common.⁶

Immediately after the acquisition, Broadcom laid off former CA workers across multiple offices.⁷ The large Computer Associates campus in Islandia, New York—once the company's headquarters—was abandoned. In January 2024, the building was demolished via controlled explosion.⁸

But port 216 remains, still officially assigned to CAIlic in IANA's registry.

Security Considerations

Port 216 has been flagged in security databases as potentially used by malware.⁹ This doesn't mean the port itself is malicious—it means that over the years, trojans and viruses have occasionally used port 216 to communicate, likely because it's an assigned but rarely scrutinized well-known port.

If you see unexpected traffic on port 216 and you're not running Computer Associates software, investigate:

# Check what's listening on port 216
sudo lsof -i :216
sudo netstat -tulpn | grep :216

# On Windows
netstat -ano | findstr :216

Related Ports

Many enterprise software vendors operated similar license servers:

• Port 27000-27009: FlexNet Publisher (FLEXlm) license management, used by Autodesk, MATLAB, and hundreds of other vendors
• Port 1947: Sentinel License Manager (formerly Sentinel RMS)
• Port 6200: Oracle License Manager

These ports all served the same purpose: connecting software to license servers that decided whether you could use what you paid for.

Why This Port Matters

Port 216 represents a specific era of enterprise software—when companies like Computer Associates dominated corporate IT with expensive, centrally managed systems. The licensing model required network infrastructure, dedicated servers, and ports like 216 to enforce compliance.

That era is fading. Computer Associates no longer exists. Cloud licensing and subscription models have largely replaced network license servers. But port 216 remains in IANA's registry, a permanent assignment from a time when enterprise software licensing required its own network protocol.

The ghost of a $18.9 billion company, preserved in a port number.