Port 3247: DVT DATA LINK — A Name Without a Story

Port 3247 sits in the registered port range (1024–49151), the middle tier of the port number system. Unlike the well-known ports below 1024 — which require root privileges on Unix systems and carry protocols that billions of people use every day — registered ports are simply names in a registry. Anyone can file a request with IANA, and if the port is available, it's theirs.

In February 2002, someone registered port 3247 under the name DVT DATA LINK. That's nearly everything that's known about it.

What DVT DATA LINK Was

The IANA record lists a contact name and a registration date. No RFC was filed. No public documentation exists. No known software claims to use it. DVT DATA LINK may have been an internal protocol for a product that never shipped, a company that no longer exists, or a tool so niche it left no trace on the public Internet.

This isn't unusual. The registered port range contains thousands of entries just like it: a name, a date, and silence.

What Actually Uses This Port in Practice

Because DVT DATA LINK is effectively dormant, port 3247 is functionally unclaimed in any meaningful sense. If you see traffic on this port, it's almost certainly one of three things:

• Custom application traffic — developers frequently bind internal services to obscure registered ports to avoid conflicts
• Malware or unwanted software — obscure port numbers are sometimes chosen specifically because they fly under the radar
• Overlap with Citrix Framehawk — Citrix NetScaler Gateway uses a broad UDP range (3224–3324) for its Framehawk virtual desktop protocol, and port 3247 falls within that window¹

How to Check What's Listening on This Port

If you see activity on port 3247 on your machine or network, these commands will tell you what's behind it.

On Linux or macOS:

# Show what process is listening on port 3247
sudo ss -tlnp sport = :3247

# Or with lsof
sudo lsof -i :3247

On Windows:

# Show listening processes with PID
netstat -ano | findstr :3247

# Match PID to process name
tasklist | findstr <PID>

Scanning from another machine:

# Check if the port is open
nmap -p 3247 <target-ip>

Why Unassigned-in-Practice Ports Matter

The port registry is not a map of what's actually running on the Internet. It's a reservation system, and many reservations were made and then abandoned. The real landscape of port usage — what software actually binds to what port — is messier, more dynamic, and only partially documented.

This gap matters for security. Firewall rules written against the official registry will miss software that ignores it. Traffic on an "unassigned" port isn't inherently suspicious, but it does warrant a look. The question is never "is this port supposed to be used?" It's "do I know why this port is active on my network?"

Port 3247 is as good a reminder as any that the registry is a starting point, not an answer.