Port 3485: CelaTalk — A Registered Port That Never Arrived

What Port 3485 Is

Port 3485 sits in the registered ports range (1024–49151). IANA assigned it to a service called CelaTalk in May 2002, and that is essentially the full extent of its documented history.

CelaTalk appears to have been a communication or messaging application. Beyond the registration, it left no public documentation, no surviving software, no RFC, and no user community. The name exists in the IANA registry on both TCP and UDP. The service itself does not appear to exist anywhere in active use.

The Registered Ports Range

Registered ports (1024–49151) are one step removed from the well-known ports (0–1023) that handle the Internet's core infrastructure. Any organization or developer can apply to register a port number in this range with IANA for a specific service. Registration means:

• The port number is reserved under that service's name
• Other services are discouraged from using it officially
• The service itself may or may not actually exist or be deployed

Registration is not the same as use. Thousands of registered ports belong to services that were abandoned, never shipped, or quietly replaced. Port 3485 is one of them.¹

What You Might Actually Find on Port 3485

Because the port has no active official service, anything listening here is either:

• Application-specific: A developer or vendor chose this port for internal use precisely because it's obscure and unlikely to conflict
• Malware or scanning activity: Attackers occasionally use unassigned ports to evade firewall rules
• Nothing: The most common answer

SANS ISC shows occasional scanning activity targeting port 3485, which is typical for any port in this range — automated scanners probe everything, regardless of whether a known service lives there.²

How to Check What's Listening on Port 3485

On Linux/macOS:

# Show what process is using port 3485
ss -tlnp | grep 3485
# or
lsof -i :3485

On Windows:

netstat -ano | findstr :3485

If nothing returns, nothing is listening. If something returns, the process name will tell you what claimed the port.

Why Unassigned and Dormant Ports Matter

Port numbers are a finite namespace — 65,535 of them, shared across every protocol and service on every machine connected to the Internet. The registered range was designed to bring order to that namespace, but the system relies on services actually using what they register.

Dormant registrations like CelaTalk occupy a number that could, in theory, be claimed by something new — but IANA's process is conservative. The ghost of a 2002 messaging app holds its spot in the registry indefinitely.

For network administrators, unassigned or dormant ports showing traffic are worth a second look. Expected traffic on a well-known port is noise. Unexpected traffic on a port that should be quiet is a signal.