Port 2542: uDraw(Graph) — The Graph Visualizer That Changed Its Name

What This Port Does

Port 2542 is registered with IANA for uDraw(Graph), a graph visualization tool developed at the University of Bremen, Germany. The tool draws automatic layouts for graphs, hierarchies, flowcharts, and diagrams, and exposes an API that lets other applications embed it as a visualization component.

You almost certainly have no process listening on this port. uDraw(Graph) was primarily an academic tool, and its registration represents a slice of 1990s university software infrastructure that rarely runs on modern systems.

The daVinci Problem

The software was originally called daVinci — a nod to its ability to render elegant diagrams automatically. It was developed in the early 1990s at Bremen, gained academic traction as a graph visualization backend, and was registered with IANA under the service name davinci at port 2542.¹

Then in 2005, a trademark conflict forced a rename. The tool became uDraw(Graph). IANA updated the official registry. But third-party port databases are slow to follow IANA changes, and some never do. The result: search for port 2542 today and you'll find it listed as "davinci" in some databases, "uDraw(Graph)" in others, and simply "unassigned" in a few that have given up tracking it.

The port is assigned. It has been for decades. The confusion is a database problem, not a protocol problem.

The Registered Port Range

Port 2542 sits in the registered port range (1024–49151), sometimes called the user ports range. These ports are managed by IANA: any organization can apply to register one for their service, which is exactly what the University of Bremen did.

Registered ports differ from well-known ports (0–1023) in one practical way: no special operating system privileges are required to bind them. Any process running as a normal user can open a server on port 2542. This makes registered ports useful for application-layer services that don't need elevated access, and also makes them popular with software that wants a stable, documented port without requiring root.²

Why Unassigned Ports Matter

Most registered ports go unused on any given system. The range covers over 48,000 ports, and IANA has assigned only a fraction. The rest sit empty — available for ephemeral application use, developer testing, or legitimate services that simply haven't registered.

This availability matters for two reasons. First, it gives applications breathing room: a service can pick an unregistered port and operate without colliding with anything official. Second, it creates ambiguity in security monitoring. When an unusual port shows activity, there's no reference point for what "normal" looks like. Port 443 being open is expected. Port 2542 being open warrants a second look.

What's Actually Listening on This Port

If you see traffic on port 2542 and you're not running uDraw(Graph) (you're not), the most likely explanations are:

• A custom application claiming the port for its own use
• A development service binding an arbitrary registered port
• A misconfigured or misbehaving process
• Port scanning noise that never resulted in a connection

To check what's listening:

# macOS / Linux
sudo lsof -i :2542

# Linux (alternative)
sudo ss -tlnp sport = :2542

# Windows
netstat -ano | findstr :2542

The process name and PID in the output will tell you exactly what's claiming the port.