Port 3615: Start Messaging Network — a ghost from the messaging wars

What This Port Is

Port 3615 sits in the registered ports range (1024–49151). These ports are assigned by the Internet Assigned Numbers Authority (IANA) to specific services upon request — no fee, no audit, just a name, a contact, and an intent. IANA registered port 3615 to Start Messaging Network in October 2002, with Peter Rocca of multiboard.com listed as the assignee.¹

That company is gone. The domain no longer resolves to anything meaningful. What remains is the registration in the IANA database and one line in port reference tables across the Internet.

The Registered Ports Range

Ports 1024–49151 occupy the middle ground of the port number space. Well-known ports (0–1023) require formal approval and administrative authority. Dynamic ports (49152–65535) are ephemeral — grabbed on the fly for outgoing connections, released when they're done.

Registered ports are somewhere in between: anyone can submit a registration, and IANA will list it. The listing doesn't mean the protocol is widely deployed. It doesn't mean the software still exists. It means someone, at some point, thought their service warranted a named slot in the registry.

Many of those registrations date from the early 2000s, when the Internet was young enough that claiming a port felt like staking land. Messaging services proliferated. Every company wanted its own protocol, its own port, its own piece of the namespace. Most of those companies are gone. The port registrations remain.

The Messaging Wars, 2002

The year port 3615 was registered, AIM had over 30 million users. MSN Messenger was fighting for the same audience. Yahoo Messenger, ICQ, and dozens of smaller services were all competing for the same eyeballs and the same habit: the persistent chat window.

Into this landscape came Start Messaging Network. The registration is all we have. No RFC, no surviving documentation, no trace of the protocol itself. Whatever it was supposed to do, it didn't outlast the decade.

What You'll Find on Port 3615 Today

Almost certainly nothing, unless something is running there by coincidence. Applications sometimes use ports from the registered range without consulting IANA — especially internal tools, development servers, or software with hardcoded port numbers that happened to land here.

If you're seeing traffic on port 3615 and wondering what it is, it isn't Start Messaging Network. It's whatever your own software is doing.

How to Check What's Using This Port

On Linux or macOS:

# Show what process is listening on TCP port 3615
ss -tlnp sport = :3615

# Or with lsof
lsof -i TCP:3615

# For UDP
lsof -i UDP:3615

On Windows:

netstat -ano | findstr :3615

Match the PID from the last column against Task Manager or:

tasklist /fi "PID eq <PID>"

If nothing appears, nothing is listening. The port is quiet.

Why Ghost Registrations Exist

IANA's registry is append-friendly and cleanup-averse. A registration requires a request; removing one requires... no one has really established a clear process. Defunct services stay listed because delisting them requires someone to care enough to ask, and the original registrant is often unreachable.

This creates a peculiar archaeology. The IANA registry contains registrations from companies that IPO'd and crashed, protocols designed for problems that got solved differently, and services that simply failed to find users. Port 3615 is one of many.

The ports aren't wasted — nothing is "using" them in any meaningful sense. They sit unclaimed in the namespace, available for anything that wants to squat there. Whether that's your development server or something else is between you and lsof.