Port 3052: Unassigned — Quietly Occupied

What Range This Port Belongs To

Port 3052 sits in the registered port range (1024–49151), sometimes called the "user ports." IANA manages this range and assigns ports to specific services by application. But registration is voluntary, and the range is large. Port 3052 has never been assigned an official service.

That doesn't mean nothing uses it.

Known Unofficial Uses

APC PowerChute Network Shutdown (UDP)

The most documented use of port 3052 belongs to APC PowerChute Network Shutdown (PCNS), software from Schneider Electric that protects servers connected to APC UPS hardware.¹

The Network Management Card (NMC) inside the UPS sends a UDP packet to port 3052 on every registered server every 25 seconds. This is the heartbeat. If those packets stop arriving — because power has failed and the UPS is running on battery — the PCNS agent on each server knows to start an orderly shutdown before the battery dies.

The packets are MD5-authenticated. The password never travels in plaintext. It's a small, tight protocol doing one important job: making sure servers die gracefully instead of abruptly.

If you run APC UPS hardware in a data center and port 3052 is blocked by a firewall, your servers won't receive shutdown notifications. They'll just go dark when the battery runs out.²

Interbase/Firebird Alternate Port (TCP)

InterBase and its open-source descendant Firebird use port 3050 by default for remote database connections.³ When that port is already occupied — by another Firebird instance, a conflict, or a deliberate security choice — administrators sometimes shift to nearby ports. Port 3052 occasionally appears in this role.

It's informal. There's no standard that says "use 3052." But if you find TCP 3052 open on a database server, an alternate Firebird instance is a reasonable explanation.

How to Check What's Listening on This Port

On Linux/macOS:

# Show what process is using port 3052
ss -tulnp | grep 3052

# Or with lsof
lsof -i :3052

On Windows:

netstat -ano | findstr :3052

Then cross-reference the process ID against Task Manager or:

tasklist /FI "PID eq <pid>"

If you see javaw.exe or a process named pcns, it's PowerChute. If you see fbserver.exe or firebird.exe, it's a Firebird instance.

Why Unassigned Ports Matter

The port system works because most software agrees to use the same ports for the same things. When a port is unassigned, nothing enforces that agreement. Two different applications can claim the same port on the same machine — and they'll conflict.

Port 3052 has stayed unassigned long enough that two distinct ecosystems quietly settled on it. That's usually how it goes: IANA didn't assign it, so real-world software did.