Port 2553: efidiningport — A Registered Ghost

What Is Port 2553?

Port 2553 sits in the registered ports range (1024–49151) — the middle tier of the port numbering system, between the well-known ports that run the core Internet infrastructure and the ephemeral ports your OS assigns on the fly for outbound connections.

Registered ports are supposed to mean something. To claim one, you file a request with IANA. You give your service a name, describe what it does, and provide a contact. IANA records the assignment, and from that point forward, that port number belongs to your service — at least on paper.

Port 2553 was claimed. Someone did all of this. And then the trail vanishes.

The efidiningport Mystery

According to the IANA Service Name and Transport Protocol Port Number Registry, port 2553 is assigned on both TCP and UDP to a service called efidiningport. The description field: also "efidiningport." The registrant contact leads to an address at execpc.com — a regional ISP based in Wisconsin that is no longer active.¹

What is efidiningport? No RFC defines it. No open-source project implements it. No vendor documentation references it. It's a name with no body attached.

The "efi" prefix could suggest a connection to EFI (Extensible Firmware Interface), but there's no evidence for that. "Dining" is harder still to explain in a networking context. The most likely answer: someone registered this port in the 1990s or early 2000s for a small application that never shipped, or shipped and died quietly, and left nothing behind.

What This Port Is Used For Today

Nothing official. In practice, port 2553 behaves as unassigned. Some security databases note historical associations with malware — this is common for obscure registered ports, since attackers sometimes choose ports that appear legitimate in registry lookups but generate no legitimate traffic to explain away.²

If you see traffic on port 2553, it's almost certainly a custom application choosing an available port, not efidiningport (whatever that was).

The Registered Ports Range

The 1024–49151 range contains about 48,000 ports. IANA has assigned most of the lower end — ports 1024–5000 or so are densely registered. Higher numbers thin out quickly. Many registered ports are exactly like 2553: claimed by someone once, never actively used, occupying a slot in a registry but doing nothing on any actual network.

This matters because port numbers carry implicit meaning. When a firewall administrator sees traffic on a registered port, they check the registry and find a name. A name suggests legitimacy. A name like "efidiningport" — meaningless enough that nobody questions it, registered enough that it doesn't trigger automatic suspicion — is precisely the kind of cover that makes obscure registered ports occasionally attractive for unauthorized uses.

How to Check What's Listening

If you see port 2553 active on a system you manage:

Linux / macOS:

# Show what process is listening on port 2553
sudo lsof -i :2553

# Or with ss (Linux):
sudo ss -tlnp | grep 2553

Windows (Command Prompt as Administrator):

netstat -ano | findstr :2553

The output will show you the process ID. From there:

• Linux/macOS: ps aux | grep <PID>
• Windows: Open Task Manager, go to Details tab, find the PID

If nothing is listening on port 2553, that's the expected state. If something is, identify it before assuming it's benign.