Port 576: ipcd — A forgotten assignment in the well-known range

Port 576 is officially assigned to ipcd (IPC Daemon), a service intended for inter-process communication.¹ It lives in the well-known port range (0-1023), which means it was assigned by IANA for a specific purpose. But here's the reality: you'll almost never see traffic on this port.

What is ipcd?

IPCD stands for IPC Daemon—a service designed to manage inter-process communication between programs. In some modern operating systems like Redox OS, ipcd handles Unix Domain Sockets, allowing processes to communicate efficiently within the same machine.²

The concept is sound: processes need to talk to each other, and a dedicated daemon could manage that communication. But in practice, most systems handle IPC through other mechanisms—shared memory, pipes, local sockets—without needing a network port at all.

Why this port exists but sits empty

Port 576 represents a category of assignments that are technically official but practically obsolete. Someone, decades ago, requested this port for their IPC implementation. IANA granted it. The assignment remains in the registry.

But the service never became widespread. Modern systems either:

• Handle IPC without network ports (using local mechanisms instead)
• Use different approaches that evolved after this assignment
• Never needed a centralized IPC daemon in the first place

So port 576 sits there, officially assigned, rarely used.

The well-known range

Ports 0-1023 are the well-known ports—assigned by IANA for standard Internet services. Getting a port in this range used to mean something. It suggested your service would be fundamental to how networks operate.

Port 576 has that assignment. But having the assignment doesn't guarantee the service will matter.

Checking if anything is using this port

To see if port 576 is actually in use on your system:

# Linux/macOS
sudo lsof -i :576
sudo netstat -tlnp | grep :576

# Windows
netstat -ano | findstr :576

Most likely, you'll see nothing. That's normal. This port is assigned but dormant on nearly every machine.

Why unassigned and dormant ports matter

The port number space is finite—65,535 ports total. Of those, the well-known range (0-1023) is the most valuable real estate. Every port assigned to a service that never took off is a number that can't be used for something else.

Port 576 is a reminder that assignments outlive relevance. The registry preserves history even when the services themselves fade away.