Port 374 is a ghost. It belongs to a company that ceased to exist nearly 30 years ago, reserved for a protocol whose purpose has been lost to time.
What Port 374 Was Assigned For
The Internet Assigned Numbers Authority (IANA) lists port 374 (both TCP and UDP) as assigned to "legent-2"—the second of two consecutive port assignments made to Legent Corporation.1 Port 373 was "legent-1."
Legent Corporation built systems management software for mainframe computers in the late 1980s and early 1990s.2 They needed network ports for their software to communicate. IANA gave them ports 373 and 374. The exact protocols that used these ports—what they did, how they worked, what problem they solved—has been forgotten.
The Company That Owned This Port
Legent was formed in 1989 by merging two mainframe software companies: Duquesne Systems and Morino Associates.3 This was the era when mainframes dominated enterprise computing, and systems management software was big business.
By 1995, Legent had grown to $502 million in annual revenue. That year, Computer Associates acquired them for $1.78 billion—the largest software acquisition in history at that time.4
Legent Corporation disappeared into Computer Associates (later renamed CA Technologies, then acquired by Broadcom). The software probably disappeared too, replaced by newer systems or simply discontinued.
But port 374 remains. Nobody returned it to IANA. Nobody unassigned it. It sits in the official registry, waiting for traffic that will never come.
What Range Port 374 Belongs To
Port 374 falls in the well-known ports range (0-1023), also called "System Ports."5 These ports require IETF Review or IESG Approval for assignment. They're supposed to be for important, widely-used protocols—things like HTTP (80), HTTPS (443), SSH (22).
Port 374 got that designation. It's officially recognized, permanently assigned. But the service it was assigned to is gone.
Why Unassigned Ports Matter (And Why This One Is Complicated)
Port 374 isn't technically unassigned—it has an official designation. But practically speaking, it's abandoned. The company doesn't exist. The software doesn't run. The protocol is unknown.
This happens more than you'd think. The Internet grew fast in the 1990s. Companies needed ports, got them assigned, then were acquired or went out of business. Their port numbers remain in the registry because there's no formal process for returning them.
Port 374 is a reminder that the Internet has archaeology. Layers of history baked into the infrastructure. Every port number tells a story, even when that story is "someone needed this once, and nobody thought to clean it up."
Checking What's Actually Using Port 374
Even though port 374 is officially assigned to a defunct protocol, something on your system might be using it. Here's how to check:
On Linux or macOS:
On Windows:
If you find something listening on port 374, it's not the original Legent software. It's either:
- A modern application that happened to use this port
- Malware (port 374 has been historically associated with trojans precisely because it's assigned but unused)6
- A misconfigured service
The Honest Reality
Port 374 is technically assigned but functionally dead. It's a memorial to Legent Corporation—a company that was significant enough to get well-known ports assigned, but not significant enough to be remembered.
The Internet is full of these digital fossils. Ports assigned to companies that no longer exist. Protocols nobody uses anymore. RFCs describing systems that were replaced decades ago.
They stay in the registries because nobody bothers to remove them. And maybe that's appropriate. The Internet has a long memory. Port 374 remembers Legent Corporation, even if we don't.
Was this page helpful?