Port 3335: Unassigned — The Squatters and the Sky

What Range This Port Lives In

Port 3335 sits in the registered ports range (1024–49151). IANA maintains this range and assigns port numbers to services that request them — things like HTTP (80), HTTPS (443), and DNS (53). But registration isn't mandatory, and IANA doesn't police squatters.

Port 3335 was never claimed. IANA lists it as unassigned.¹

Who's Using It Anyway

Despite the vacancy, two distinct pieces of software have quietly moved in.

DirectTV Software Updates

Port 3335 (TCP and UDP) appears in security databases as associated with DirectTV satellite receiver software updates.² The mechanism: DirectTV set-top boxes open connections on this port to check for and download firmware updates. It's not documented in any RFC or official standard — it's just what the software does.

UgCS Drone Ground Control (DJI)

UgCS, a professional drone flight planning platform from SPH Engineering, uses TCP port 3335 as its VSM (Vehicle Specific Module) connection port for DJI aircraft.³ When you run UgCS on a desktop and pair it with the UgCS for DJI mobile app, the drone controller connects back to the UgCS server on port 3335. The configuration lives in ucs.properties as ucs.vsm.server.port=3335.

Two completely unrelated applications. Same port. No conflict because you're unlikely to run satellite TV update software and a drone ground station on the same machine.

How to Check What's Listening

If you see port 3335 active on a system you're responsible for, these commands will tell you what's using it:

macOS / Linux:

# Show the process listening on port 3335
sudo lsof -i :3335

# Or with ss (Linux)
sudo ss -tlnp | grep 3335

Windows:

# Show process ID using port 3335
netstat -ano | findstr :3335

# Look up the process by PID
tasklist | findstr <PID>

If neither DirectTV software nor UgCS is installed and port 3335 is open, dig deeper. Unknown open ports are worth understanding.

Why Unassigned Ports Matter

The registered port range has 48,128 slots. Fewer than 10,000 are officially assigned. The rest are exactly like port 3335 — unclaimed territory where applications self-assign without coordination.

This isn't chaos, exactly. It works because most port collisions never happen in practice. Your drone software and your satellite TV receiver don't run on the same host. But when they do collide, there's no arbitration — whoever starts first wins, and the other fails silently or picks a different port.

Unassigned ports remind you that the port numbering system is less a carefully managed resource and more a loose convention held together by the fact that most software doesn't overlap.