Port 1800: Registered, Rarely Recognized

What Range This Port Belongs To

Port 1800 sits in the registered ports range (1024–49151). IANA manages this space: organizations can apply to claim a port number for their software, and IANA records the assignment in its official registry.

Registered doesn't mean reserved. It means someone asked, and IANA said yes. The port isn't locked — any software can use it. The registration is more like a street address in a phone book than a deed to property.

The Official Assignment

IANA's registry lists port 1800 as ANSYS-LM — supposedly for the ANSYS license manager.¹ ANSYS makes widely-used engineering simulation software (finite element analysis, fluid dynamics, that kind of thing). License managers control how many simultaneous users can run expensive software.

The catch: ANSYS's actual license manager uses port 1055, not 1800.² The ANSYS-LM registration on port 1800 appears to be a historical artifact that never caught on in practice. The software went one way; the registration stayed put.

What Actually Uses Port 1800

In the wild, port 1800 shows up in a few places:

Snom VoIP Phones The Snom 320 SIP phone runs its web administration interface on port 1800. Multiple security vulnerabilities were documented against it, including the ability to place calls and access call history without authentication.³

Netgain Enterprise Manager This network management platform listens on TCP ports 1800 and 1850 for its RMI registry. A deserialization vulnerability (CVE-2017-17406) allowed unauthenticated remote code execution through this port.⁴

W32.Wowinzi.A A 2008 worm that spread via removable drives was documented communicating over port 1800. This is the kind of port that malware likes — obscure enough that firewall rules rarely block it explicitly.⁵

None of these uses have anything to do with ANSYS.

How to Check What's Listening on Port 1800

If you see traffic on port 1800 and want to know what's using it:

On Linux/macOS:

# Show what process is listening on port 1800
ss -tlnp | grep 1800

# Or with lsof
lsof -i :1800

On Windows:

# Show listening ports with process IDs
netstat -ano | findstr :1800

# Then look up the PID
tasklist | findstr <PID>

If something is listening on port 1800 and you didn't put it there, it's worth investigating. The legitimate software that uses this port is uncommon enough that an unexpected listener is unusual.

Why Unassigned-ish Ports Matter

Port 1800's situation illustrates something real about the port system: the registry is imperfect. Registrations get made and forgotten. Software evolves and moves. The gap between "what IANA says" and "what actually runs" on a given port can be wide.

This matters for security. Firewalls that block "unregistered" ports won't catch traffic on a registered-but-obscure port like 1800. Attackers know this. A port that exists in IANA's registry but doesn't appear in most threat intelligence lists is exactly the kind of port that can hide things.