Port 2866: iwlistener — Registered, But Unknown

What Port 2866 Is

Port 2866 sits in the registered ports range (1024–49151). These ports are assigned by IANA upon application — meaning someone formally requested this port number, submitted a contact name, and IANA recorded it.

The recorded assignment: iwlistener, contact Fred Surr, for both TCP and UDP.¹

What "iwlistener" does? Nobody seems to know. There is no public RFC, no open-source project, no vendor documentation, no forum post explaining this service. The IANA entry lists the service name and nothing else. Whatever iwlistener was meant to be, it never made it into the public record.

For practical purposes, port 2866 is unoccupied.

What the Registered Range Means

The registered ports (1024–49151) require a formal application to IANA. They sit between the well-known ports (0–1023), which require root privileges to bind on most Unix systems, and the ephemeral ports (49152–65535), which are used for temporary client connections.

Registered ports don't require special OS privileges to use. They also don't come with enforcement — nothing stops an application from binding to any registered port, assigned or not. The registry is a coordination mechanism, not a lock.

This means that if you see traffic on port 2866 on your network, it isn't iwlistener. It's something specific to your environment — a custom application, a development service, or possibly something you'd want to investigate.

What to Do If You See This Port in Use

If a process is listening on port 2866 on your machine, you can identify it:

On Linux or macOS:

# Show what's listening on port 2866
ss -tlnp sport = :2866

# Or with lsof
lsof -i :2866

On Windows:

netstat -ano | findstr :2866

The output will give you a process ID (PID). Match it against your running processes to identify the application.