Port 2739: Unassigned — An Empty Room in the Registered Range

What Port 2739 Is

Port 2739 is unassigned. IANA — the Internet Assigned Numbers Authority, the body that maintains the official port registry — lists no service for this port.¹

It has no RFC. No protocol was designed for it. No company has registered a claim.

Where It Lives: The Registered Port Range

Ports are divided into three ranges:

Port 2739 sits in the registered range. This range exists so software vendors can claim a consistent port number for their applications — your database, your game server, your monitoring agent. They file with IANA, IANA records the assignment, and the port becomes theirs by convention (not by enforcement).

No one has claimed 2739.

Unofficial Uses

No commonly observed unofficial uses have been documented for port 2739. It does not appear in malware databases, game server lists, or known application configurations. It is genuinely unclaimed space.

If you are seeing traffic on port 2739, it is almost certainly a private application using it by internal convention — which is perfectly legal and common. Applications can bind to any unassigned port they choose. They just won't have IANA's blessing or recognition.

How to Check What's Listening on This Port

If you need to investigate port 2739 on a specific machine:

Linux/macOS:

# Show what process is listening on port 2739
ss -tlnp | grep 2739

# Or with lsof
lsof -i :2739

Windows:

netstat -ano | findstr :2739

The output will show the process ID (PID) if anything is bound. You can then look up that PID in Task Manager or with ps aux on Unix systems.

Remotely:

# Test if the port is open from another machine
nc -zv <host> 2739

# Or with nmap
nmap -p 2739 <host>

Why Empty Ports Matter

The port system works because most ports are quiet. When a port is genuinely silent, any traffic on it is immediately suspicious. Security tools and firewalls depend on this baseline: known ports should carry expected traffic, unknown ports should carry nothing.

An unassigned port that suddenly shows activity is a signal worth investigating — not because 2739 is dangerous, but because unexpected is always the first word in every security incident.