What Port 3291 Is
Port 3291 is registered with IANA under the name sah-lm — S.A. Holditch & Associates License Manager. 1
S.A. Holditch & Associates was a petroleum engineering consulting firm founded in 1977 by Stephen Holditch in College Station, Texas. They built software for oil and gas reservoir analysis: fracture treatment design, pressure test analysis, well completion modeling. The kind of specialized engineering tools that ran on workstations in the late 1980s and early 1990s and needed a license server to enforce seat counts.
Schlumberger acquired the firm in 1997. By 1999, it had been folded into a broader Schlumberger group called Holditch Reservoir Technologies. 2 The original company, its software, and its license manager effectively ceased to exist as independent entities.
The port registration remained.
What Range This Port Belongs To
Port 3291 sits in the registered port range (1024–49151). These ports are not controlled by the operating system the way well-known ports (0–1023) are — any process can bind to them without elevated privileges. IANA maintains a registry of claimed assignments in this range, but registration is voluntary and enforcement is nonexistent. Companies could request a port number for their software, and many did.
The registered range is full of entries like this one: real assignments made for real software that either no longer ships, was never widely deployed, or has long since migrated to different ports. They're not wrong, exactly. Just orphaned.
Is Anything Using This Port Today?
Probably not — at least nothing related to S.A. Holditch software. The license manager it was registered for hasn't been actively maintained as an independent product in over 25 years.
If you see traffic on port 3291 on your network, it's something else entirely: custom internal applications, development servers, or software that picked the port informally. The Citrix NetScaler Gateway uses a range spanning ports 3224–3324 for Framehawk virtual desktop traffic, which technically includes 3291, though specific assignment within that range varies by deployment. 3
How to Check What's Listening on This Port
On Linux or macOS:
On Windows:
To identify the process by PID (Linux):
If nothing appears, nothing is listening. That's the expected result.
Why Orphaned Ports Matter
The IANA registry isn't a lease — it's closer to a deed with no expiration. When a company registers a port and then disappears, the registration doesn't automatically free up. This creates friction: new software that wants to use a port "officially" has to pick one that isn't already claimed, even if the claimed port has been dark for decades.
In practice, most software doesn't bother with formal registration. It just picks a number that seems unlikely to conflict and ships. The registered range has become partly formal record, partly historical artifact, and partly suggestion. Port 3291 is a small example of all three.
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