Port 23563: Unassigned — Unclaimed Territory

Port 23563 has no official service assigned to it. No RFC defines what runs here. No protocol claims this number. It's unclaimed territory in the Internet's address space.

The Registered Ports Range

Port 23563 falls in the registered ports range (1024-49151) — sometimes called "user ports."¹ This range sits between the well-known ports (0-1023) that require root privileges and the ephemeral ports (49152-65535) that get assigned dynamically.

The registered range exists for applications that need a consistent, known port number but don't qualify for the prestigious well-known range. Any organization can apply to IANA to register a port in this range. The process takes 1-2 months and requires IETF Review, IESG Approval, or Expert Review.²

Port 23563 hasn't gone through that process. It remains unassigned.

What Might Be Using It

Just because a port is unassigned doesn't mean nothing uses it. Port 23563 could be:

• Running a private application — Internal corporate software that never needed public registration
• Serving as a temporary listener — Development servers, testing tools, or custom scripts
• Completely unused — Just another number in the range, waiting
• Claimed informally — Some application using it without official IANA registration

The registered range contains 48,128 possible port numbers. Most of them sit unassigned, like 23563. They're not broken. They're available.

How to Check What's Listening

If you see port 23563 active on your system, here's how to find out what's using it:

On Linux or macOS:

# See what's listening on port 23563
sudo lsof -i :23563

# Or use netstat
netstat -an | grep 23563

# Or use ss (modern replacement for netstat)
ss -tuln | grep 23563

On Windows:

# Check TCP connections
netstat -ano | findstr "23563"

# Or use PowerShell
Get-NetTCPConnection -LocalPort 23563

These commands will show you the process ID and program name of whatever is using the port.

Why Unassigned Ports Matter

The existence of unassigned ports like 23563 is actually important. They represent:

Flexibility — Developers can use these ports for testing and development without conflicting with established services.

Room for growth — The Internet can evolve. New protocols can emerge without having to displace existing ones.

Private services — Organizations can run internal applications on unassigned ports without going through the formal IANA registration process.

The well-known ports (0-1023) are famous. Port 80 for HTTP. Port 443 for HTTPS. Port 22 for SSH. Everyone knows these.

But the registered range is different. It's where the long tail lives — the specialized protocols, the niche applications, the services that matter to specific communities but not to everyone. Port 3306 for MySQL. Port 5432 for PostgreSQL. Port 27017 for MongoDB.

And then there are ports like 23563. Unassigned. Unclaimed. Waiting.

The Beauty of Empty Space

Not every port needs a story. Not every number needs a protocol attached to it. The unassigned ports are the Internet's negative space — the silence between notes that makes the music possible.

Port 23563 might never have an official assignment. It might never carry a protocol that millions of people depend on. It might spend its entire existence as an empty address in a registry.

And that's fine. The Internet doesn't need all 65,535 ports to be occupied. It needs room to breathe, space for experiments, addresses available when someone builds something new.

Port 23563 is that space. Unclaimed. Unreserved. Ready.

Related Ports

Other unassigned ports in the registered range share this same status — no official service, but potentially running something private or sitting empty:

• Port 23562 — Also unassigned
• Port 23564 — Also unassigned
• Port 23565 — Also unassigned

The registered range is full of these quiet neighbors, each an unclaimed address in the Internet's vast postal system.