Port 3037: Unassigned — the Lighting Board's Quiet Port

What Port 3037 Is

Port 3037 sits in the registered port range (1024–49151). IANA maintains this range and assigns official service names to ports within it — but port 3037 has never been claimed. No RFC defines it. No protocol owns it. On paper, it is empty.¹

In practice, it is not.

Who Actually Uses It

Starting in version 3.1.0, ETC Eos — the lighting console software used in theaters, concert halls, and broadcast studios worldwide — adopted port 3037 as its fixed third-party TCP port for OSC (Open Sound Control) communication.²

OSC is a protocol for controlling media devices over a network. When a stage manager triggers a lighting cue from QLab, or when Moving Light Assistant syncs with an Eos console, that command often travels over TCP on port 3037.³

ETC also uses port 3032 for OSC, but 3037 is specifically designated for third-party integrations — software and devices outside the ETC ecosystem that need to send commands to or receive data from the console. The distinction matters in practice: certain internal Eos features (like Magic Sheet command objects) work on 3032 but not 3037.⁴

In short: if you see traffic on port 3037 in a theatrical or live-event environment, it is probably an Eos console receiving OSC messages.

What the Registered Range Means

The registered port range exists because the well-known ports (0–1023) ran out of room for every legitimate application that needed a consistent, findable address. IANA opened the registered range so software vendors could request dedicated ports, reducing collisions.

The catch: registration is voluntary. Applications can use any port in this range without registering. And many do. Port 3037 is one of hundreds of registered-range ports that are technically unassigned but functionally claimed by specific software communities.

Security Considerations

Unassigned ports are not inherently dangerous, but they warrant attention:

• Unexpected traffic on port 3037 outside a theatrical or show-control context has no obvious legitimate explanation. Investigate it.
• Firewall rules should block 3037 on systems where Eos or OSC tools are not in use. There is no reason to leave it open.
• Some port-scanning databases flag 3037 as having appeared in historical malware traffic — a pattern common to many unassigned ports, since attackers also reach for unclaimed space. This does not make 3037 inherently suspect, but it does mean unrecognized traffic here should not be ignored.

How to Check What Is Listening

macOS / Linux:

# Show what process is listening on port 3037
sudo lsof -i :3037

# Alternative using ss (Linux)
ss -tlnp | grep 3037

Windows:

netstat -ano | findstr :3037

The output will show the process ID (PID). Cross-reference it with Task Manager (Windows) or ps aux | grep <PID> (macOS/Linux) to identify the application.

If nothing is listening, the port is closed and unreachable. That is the expected state on most systems.

Why Unassigned Ports Matter

The port number system is, at its core, a coordination mechanism. Two applications cannot share a port on the same machine without conflict. IANA's registry is the agreement that prevents chaos — a shared ledger where vendors declare "this is ours."

But the ledger is incomplete. Thousands of ports in the registered range are officially unclaimed while being functionally occupied by real software in real production environments. Port 3037 is a small example of how the Internet actually works: not purely by formal assignment, but by a mix of official registration, community convention, and whoever got there first and stuck around.

In theaters running Eos, 3037 is as well-known as any named port. Outside that world, it is invisible. The Internet is full of these local dialects — ports that mean nothing globally and everything locally.