Port 3096: ndl-aps — A Name in the Registry, Nothing at the Door

What Port 3096 Is

Port 3096 sits in the registered ports range (1024–49151). These are ports that organizations and developers can formally request from IANA to associate with a specific service. Unlike the well-known ports below 1024, no special system privileges are required to open a registered port — any process can bind to one.

IANA lists port 3096 as assigned to ndl-aps (NDL Active Print Server) on both TCP and UDP. That's where the paper trail ends. There is no RFC for ndl-aps, no deployed software that identifies itself by that name, and no community of users who recognize it. It's a registration without a product — or at least, without one that ever became visible.

This happens more than you'd expect. The registered port range reflects decades of requests from vendors, startups, and projects that staked a claim and then went quiet. The port number is reserved; the service is gone.

Known Unofficial Uses

Port 3096 has no widely documented unofficial use. It falls within the range 3074–3174 that Ubisoft's Rainbow Six Vegas used for game traffic over UDP — but that overlap is incidental, not intentional, and that game's servers have been offline for years.

If you're seeing traffic on port 3096, it's worth investigating. Custom internal applications, development servers, and tunneling software will use unoccupied registered ports when they need a predictable number that isn't already taken by something well-known.

How to Check What's Using It

On Linux or macOS:

# Show what process is listening on port 3096
ss -tlnp | grep 3096

# Or with lsof
lsof -i :3096

On Windows:

netstat -ano | findstr :3096

The PID in the output can be matched to a process name in Task Manager or with:

tasklist | findstr <PID>

Why Unassigned Ports Matter

The registered port range exists so that services have stable, predictable addresses — a way for software to say "I'll be here" and for firewalls to be configured accordingly. When a port is registered but dormant, it creates a small buffer of comfort: it's unlikely to collide with something widely deployed.

That's not a guarantee. Firewall rules, container networking, and development environments all allocate ports dynamically. If you're building something internal that needs a fixed port, an unused registered number like 3096 is a reasonable choice — just don't assume the IANA registration offers any real protection from conflict in practice.