Port 3357: Adtech Test IP — A Name Without a Story

What This Port Is

Port 3357 sits in the registered port range (1024–49151). These ports are assigned by IANA, the organization that keeps the Internet's numbering system from descending into chaos. Unlike the well-known ports (0–1023), which require root privileges to bind on Unix-like systems and host the protocols everyone depends on, registered ports are claimed by specific applications and services — hundreds of them — most of which you will never encounter.

IANA lists port 3357 as "Adtech Test IP", registered to a person named Robin Uyeshiro for both TCP and UDP. That's the complete public record. No RFC. No documentation. No specification. No trace of what "Adtech Test IP" does, what it tested, or whether it was ever deployed at any meaningful scale. The name suggests something in advertising technology infrastructure — a test endpoint of some kind — but the silence around it is total.

This happens. Someone files a port registration, sometimes to reserve a number for internal tooling, sometimes for a product that never shipped, sometimes for a service that ran quietly behind closed doors. IANA's registry is a historical record as much as an active directory. Port 3357 is a footnote with no article attached.

Is Anything Using This Port?

Almost certainly not the registered service. If something is listening on port 3357 on your system, it's either:

• An application that chose this port arbitrarily — many services pick numbers in this range without checking the registry
• A game server or development tool using the port by convention within a specific community
• Malware — security databases have flagged this port in the past as occasionally used for command-and-control traffic, though this is not specific to port 3357 and reflects the general pattern of malware using obscure registered ports to blend in

How to Check What's Listening

On Linux or macOS:

ss -tlnp | grep 3357

Or with the older tool:

netstat -tlnp | grep 3357

On Windows:

netstat -ano | findstr :3357

This shows you the process ID (PID) bound to the port. Then:

# Linux/macOS - identify the process
ps aux | grep <PID>

# macOS alternative
lsof -i :3357

# Windows - identify the process
tasklist | findstr <PID>

If you find something listening here that you didn't expect, that's worth investigating. An unknown process on an obscure registered port is exactly the kind of thing you want to understand.

Why Ports Like This Exist

The registered port range has over 48,000 numbers. IANA has assigned names to thousands of them. Many of those assignments represent real, active protocols. Many others are like port 3357 — claimed once, documented minimally, and left to the archive.

This is actually useful. The registration system means that even obscure internal tools can stake a claim to a number, reducing the chance that two different services will inadvertently collide on the same port. The alternative — everyone just picking numbers freely — would work fine locally but becomes a problem the moment two services need to coexist.

Port 3357 is registered. Registered means claimed, not necessarily used. The Internet is full of claimed things.