Port 10523 — Unassigned, Waiting

What This Port Is

Port 10523 is a registered port—one of 48,127 ports (1024-49151) that IANA designates for applications to request. Unlike the well-known ports (0-1023) that are pre-assigned to famous protocols like HTTP, SMTP, and SSH, registered ports are up for grabs. Someone can petition IANA to register a service here. If approved, it's official. If not requested, it stays empty.

Port 10523 has no official assignment. ¹ It sits in the registry unregistered, which means any application can use it, and usually nobody notices.

What Actually Uses It

In practice, port 10523 gets borrowed by specialized tools that need a listening port and don't care about standards:

Google Chronicle uses port 10523 on localhost (127.0.0.1) for NIX_SYSTEM collection—a local sink for Linux authentication logs. It's not broadcasting it to the Internet. It's just there, on your machine, if you're running Chronicle's security platform.

rsyslog configurations sometimes forward logs to port 10523 on a local collector. System administrators set this up when they need to split syslog traffic and pick an available port. They chose 10523 because it was free.

These aren't official uses. They're practical uses. No RFC. No specification. Just applications saying "this port is open, so I'll use it."

Checking What's Listening

If you see port 10523 active on your system and want to know what's using it:

On Linux or macOS:

lsof -i :10523                    # Show process using this port
netstat -tuln | grep 10523        # Show listening sockets
ss -tuln | grep 10523             # Modern alternative to netstat

On Windows:

netstat -ano | findstr :10523     # Show process ID using this port

Then use the process ID to identify the application. If it's something you didn't install, that's interesting. If it's Chronicle or a logging system you set up, you're fine.

Why Unassigned Ports Matter

The port system works because most applications respect the assignments. Port 443 means HTTPS. Port 22 means SSH. Port 25 means SMTP. This shared understanding is what makes the Internet work.

But the system also allows for overflow and flexibility. When a startup needs a port for their internal tool, they don't petition IANA. They pick an unassigned registered port and use it. It works fine locally. It works fine on private networks. The official system stays clean while the practical world keeps moving.

Port 10523 is one of thousands like this—legitimately empty, occasionally occupied, never famous. It's the silence between the notes.

Related Ports

• Ports 1024-49151: All registered ports (mostly unassigned like this one)
• Ports 49152-65535: Dynamic/ephemeral ports (no one even tries to assign these)
• Port 514: Syslog (the official logging port, if you need to know where this lives in the hierarchy)

The Truth

Port 10523 doesn't have a story because it doesn't have a protocol. If you find it listening on a system you don't recognize, check what's using it. If it's something you installed, it's fine. If it's not, it might be worth investigating. But most of the time, port 10523 is just quiet background infrastructure, doing a job too small to have a name.