What This Port Does
Port 3697 is registered with IANA as nw-license — the network license server for Autodesk NavisWorks, a construction coordination platform used to review 3D building models, detect clashes, and manage project timelines.
When a firm runs NavisWorks on a network license, the software checks in with a license server before it opens. That check-in happens over port 3697. The server says: yes, there's a seat available, you may proceed. Or: no seats left, try again later.
It is, in the taxonomy of ports, a license gatekeeper for a niche tool used by people building physical things.
The Software Behind the Port
NavisWorks was originally developed by a UK company called NavisWorks Limited and acquired by Autodesk in 2007. The software is used in AEC (Architecture, Engineering, Construction) workflows — specifically for "clash detection," finding places in a 3D building model where, say, a ventilation duct would pass directly through a structural beam. Catching that problem in software is considerably cheaper than catching it on the job site.
The IANA registration for port 3697 predates the Autodesk acquisition, registered under the original company name around 2003. 1
What Range This Port Belongs To
Port 3697 sits in the registered port range (1024–49151). IANA maintains this range for applications that need a consistent, known port but don't rise to the significance of a well-known port (0–1023). 2
Registered ports don't require elevated system privileges to open, and they're not reserved the way well-known ports are. Any application can technically use any registered port — IANA registration is a coordination mechanism, not enforcement.
Who Actually Sees This Port
Almost nobody, unless you work in construction, architecture, or engineering IT. If port 3697 is open on a machine on your network, it's almost certainly a NavisWorks license server — the kind of thing set up once, forgotten, and quietly doing its job for years.
If you see it somewhere unexpected, that's worth investigating.
How to Check What's Listening
Linux / macOS:
Windows (Command Prompt as Administrator):
Quick scan from another machine:
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