Port 3706: rt-event — A Name with No Protocol

What Port 3706 Is

Port 3706 sits in the registered ports range (1024–49151). These are ports that individuals and organizations can apply to IANA to have assigned to their software or protocol. Unlike the well-known ports below 1024 — which carry HTTP, SSH, DNS, and the other load-bearing infrastructure of the Internet — registered ports are claimed by whoever asks.

Someone asked for port 3706 in February 2003. IANA assigned it the service name rt-event, short for "Real-Time Event Port." Its neighbor, port 3707, was registered at the same time as rt-event-s — the secure variant.¹

And then, apparently, nothing happened.

What rt-event Was Supposed to Be

The IANA registry lists the registrant as Terry Gin, circa 2003. That's essentially all the documentation that exists. There is no RFC. There is no protocol specification. There is no software repository, no vendor documentation, no forum post asking why it's blocked by a firewall. Whatever "Real-Time Event Port" was meant to carry, it never made it into production — or if it did, it disappeared entirely.

This is more common than you might expect. The early 2000s saw a wave of port registrations from software projects and startups that either never shipped, were acquired, or simply quietly wound down. The IANA registry preserves their names like fossils — evidence of intent, without evidence of life.

What Might Actually Be Listening on Port 3706

Because the official protocol never materialized, port 3706 has no canonical software that uses it. If you see something listening on this port, it's almost certainly:

• Custom application software — internal tooling or proprietary services that picked this port arbitrarily or for their own reasons
• A misconfigured or mislabeled service — some port scanners or inventory tools will try to label traffic on 3706 as "rt-event" based on the IANA name, which tells you very little
• Malware or unauthorized processes — any unrecognized open port deserves scrutiny

How to Check What's Listening

On Linux or macOS:

# Show what process is listening on port 3706
ss -tlnp sport = :3706

# Or with lsof
lsof -i :3706

On Windows:

# Find what's listening on port 3706
netstat -ano | findstr :3706

# Then match the PID to a process
tasklist | findstr <PID>

With nmap, to probe from outside a machine:

nmap -sV -p 3706 <target>

The -sV flag attempts service version detection — useful for identifying what's actually running, rather than what IANA says should be running.

Why Ghost Ports Matter

The registered port space is not a tight ledger. IANA doesn't verify that registered protocols are ever implemented, maintained, or used. Over the decades, hundreds of ports have been assigned to projects that never launched or companies that no longer exist.

This matters because unverified port registrations create noise. When a firewall rule mentions "rt-event," or a security scanner flags port 3706, the natural assumption is that there's a real protocol with real documentation to consult. There isn't, here. You're on your own to determine what's actually running.

Port 3706 is a small reminder that the port registry is a historical record as much as a technical one. Every ghost port is a story that didn't finish.