Port 1641 sits in the registered ports range (1024-49151), where IANA assigns port numbers to specific services. According to the official registry, port 1641 belongs to something called "InVision."1
But here's the reality: if you see port 1641 active on your network, it's probably not InVision. It's more likely Autodesk's network licensing system talking to a license server.2
What Range This Port Belongs To
Port 1641 is a registered port. The registered range (1024-49151) is maintained by IANA, where organizations can apply to have a port number officially assigned to their service. Unlike well-known ports (0-1023), registered ports don't require root or administrator privileges to bind to.
The idea is simple: if you're building a service that needs a standard port number, you register it with IANA so everyone knows what that port is for. In practice, the system works better for some ports than others.
The Official Assignment: InVision
IANA officially assigned port 1641 to a service called "InVision."3 Both TCP and UDP port 1641 carry this designation in the registry.
What InVision actually is—or was—remains unclear. There's an InVision design collaboration platform that exists today, but it doesn't appear to use port 1641.4 The original InVision service that secured this port assignment may be defunct, or it may have been something entirely different that shared the name.
This happens. Services disappear. Companies fold. Software gets discontinued. But the port assignment remains in the registry, a fossil of something that once needed a number.
The Actual Use: Autodesk Network Licensing
In the real world, port 1641 is more commonly associated with Autodesk products—AutoCAD, Revit, and other software in their ecosystem that uses network licensing.2
When you run Autodesk software with a network license, your computer needs to communicate with a license server to check out a license. That communication happens over specific ports. While Autodesk's primary license manager ports are 27000-27009 and 2080,5 some Autodesk-related services have been observed using port 1641.
This isn't an official Autodesk documentation fact—it's what people report seeing in the wild. Network administrators troubleshooting license server connectivity. Security teams reviewing firewall logs. The collective knowledge of people who actually maintain these systems.
Why This Matters
Port 1641 demonstrates a fundamental truth about the port system: official assignments and actual usage don't always align.
IANA provides order—a central registry where you can look up what a port is supposed to be for. But it can't enforce compliance. If software decides to use a port for something else, nothing stops it. Especially if the original assigned service isn't actively using that port anymore.
This creates ambiguity. When you see port 1641 open on a system, what is it actually doing? The registry says InVision. The forums say Autodesk licensing. Both could be true. Neither could be true—it could be something else entirely.
The only way to know for certain is to check.
How to Check What's Listening on Port 1641
On Linux or macOS:
Or with netstat:
On Windows:
This shows you the process ID (PID) of whatever is using the port. Then:
That tells you the actual program. Not what IANA says should be there. What's actually there.
The Gap Between Assignment and Reality
Port 1641 isn't unique in this regard. The registered ports range is full of assignments that made sense when they were created but don't reflect current usage. Services that moved to different ports. Companies that went out of business. Protocols that nobody uses anymore.
The registry preserves history, but it doesn't always describe the present.
When you're securing a network or troubleshooting connectivity, you can't just trust the official list. You have to verify what's actually running. The port number tells you where to look. The process list tells you what you found.
Port 1641: officially InVision, unofficially Autodesk licensing, actually whatever happens to be bound to it on your particular system. Check before you assume.
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