Port 10518 — Unassigned but in Use

What This Port Is

Port 10518 lives in the registered port range (1024–49151). These are ports for which applications can request official IANA registration, but registration is optional. Many registered ports carry official service names. Port 10518 is not one of them.

It has no IANA entry. No RFC. No official assignment. But on networks running certain monitoring infrastructure, it is very much alive.

The Unofficially Official Uses

Datadog Agent log collection — When Datadog configures Jenkins log collection, port 10518 is the default TCP port for delivery. Not documented in the official port registry, but documented in Datadog's integration setup. ¹

Symantec Syslog Director — Syslog Director 4.3 uses port 10518 as the Generic Syslog event Collector port. A security appliance claiming an unregistered port for the job it needs to do. ²

These aren't documented in any official registry because no one filed for the registration. The applications just use it. This is how much of the Internet actually works.

Why This Matters

The registered port range (1024–49151) contains 48,127 possible ports. Only a fraction are officially registered. This creates a space where:

• Applications that need network ports but don't want IANA bureaucracy simply pick one and start using it
• If two applications pick the same port, they fail to coexist on the same machine
• Port allocation becomes a local problem, not a global one
• Monitoring tools must be configured to know which port their application chose

It's decentralized. It's messy. It works.

How to Check What's Listening

On macOS:

lsof -i :10518
netstat -an | grep 10518

On Linux:

ss -tlnp | grep 10518
netstat -tlnp | grep 10518

On Windows:

netstat -ano | findstr :10518
Get-NetTCPConnection -LocalPort 10518

If nothing appears: the port is quiet. If something appears: an application claimed it and is listening. Cross-reference against your installed applications.

The Port System's Architecture

• Well-known ports (0–1023): Assigned by IANA for system services (HTTP, SMTP, DNS, SSH). Universal.
• Registered ports (1024–49151): Can be registered with IANA, but don't have to be. Semi-official.
• Dynamic/ephemeral ports (49152–65535): Temporary, assigned by the OS. The Internet's scratchpad.

Port 10518 is in the middle—legitimate enough to use, anonymous enough to not require permission. It's where monitoring tools, logging services, and proprietary applications conduct their business without asking for a name.

Sources:

• Port 10518 Information
• Datadog Agent Jenkins Collection
• IANA Service Name and Transport Protocol Port Number Registry
• SpeedGuide Port 10518