Port 3634: hNTSP Library Manager — A Ghost Registration

What Port 3634 Is

Port 3634 sits in the registered port range (1024–49151). These ports aren't reserved like the well-known ports below 1024, but organizations can formally claim them through IANA to signal "this port belongs to our protocol."

IANA's registry shows port 3634 assigned to hNTSP Library Manager (service name: hlibmgr), registered on both TCP and UDP in November 2002.¹ The registrant was Kenji Tetsuyama, with a contact address at onkyo.co.jp — Onkyo, the Japanese audio and electronics company.

What hNTSP stands for, what the Library Manager managed, and whether this software ever shipped to anyone outside Onkyo's internal network: unknown. No RFC was ever filed. No public documentation exists. No software package references this port number. It's a registration with no product behind it — or at least no product anyone can find.

What This Means in Practice

A registered port assignment is a declaration of intent, not a guarantee of use. IANA doesn't audit whether services actually run on their registered ports, and they don't reclaim abandoned registrations on any predictable schedule.

Port 3634 falls into a common category: zombie registrations. Claimed during the early 2000s when software projects were ambitious, companies were expanding into network software, and the future looked a certain way. Many of these ports were never used externally. Many of the projects behind them quietly disappeared.

If you see traffic on port 3634, it isn't hNTSP Library Manager. It's something local — a development server, a game, an application that picked this number arbitrarily because it happened to be free.

How to Check What's Using This Port

On macOS or Linux:

# Show what process is listening on port 3634
lsof -i :3634

# Or with ss (Linux)
ss -tlnp | grep 3634

On Windows:

netstat -ano | findstr :3634

The PID in the output maps to a process you can look up in Task Manager. Whatever it is, it's yours — not a known public service.

Why Unassigned Ports Matter

The registered port range exists to prevent collisions. Without it, two applications on the same machine could both try to bind port 3634 and conflict. When an application chooses a port, registering it with IANA signals to other developers: "we're here, pick something else."

The system works reasonably well for active, widely-deployed protocols. For ghost registrations like port 3634, it mostly means the port sits empty in the registry while applications that need a non-conflicting port quietly check whether anything's actually there and move on.

The port is, for all practical purposes, unoccupied. Use it accordingly.