Port Range: 1024-49151 (Registered Ports)
Port 10004 lives in the registered port range—the space between system ports (0-1023) and ephemeral ports (49152-65535). These ports are assigned by IANA, but only upon request by vendors and organizations who need a standard. The registry exists. The assignments happen. But plenty of port numbers in this range remain unassigned, waiting for someone to claim them.1
Port 10004 waited and never got claimed officially. So everyone else did instead.
The Applications That Claimed It
N-able N-central uses port 10004 for agent-to-probe communication—allowing N-able's remote management software to cache software updates across your network.2
Windows Device Association Host (dasHost.exe), a Windows system service related to device pairing, sends UDP broadcasts over port 10004 in Windows 24H2 when Protected Print Mode is enabled. Users reported these broadcasts as anomalies, not understanding why their system was talking to port 10004 at all.3
Local WordPress, the macOS WordPress development environment, runs on port 10004 for wp-admin access. Developers spinning up local WordPress sites get this port automatically, with no conflict because most development machines don't run N-able agents.4
Three different companies. Three different purposes. One port number. No coordination.
The Risk of No Assignment
When a port is unassigned, anyone can use it. This creates two problems:
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Accidental conflict — You run WordPress dev locally while N-able runs your patch management. Both want port 10004. One loses.
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Security ambiguity — When a port has no official purpose, a scanner sees traffic on it and doesn't know if it's legitimate. This can trigger false alarms.5
The IANA registry doesn't assign every possible port. It can't. But ports that remain unassigned become shared property—owned by whoever implements support first. Adoption becomes de facto standardization.
How to Check What's Listening
On macOS/Linux:
On Windows:
This shows you what process owns port 10004 on your machine. If nothing appears, the port is quiet. If something does, now you know what's trying to talk.
Why Unassigned Ports Matter
The port system works because of the registry. It's the phone book. When that phone book has blanks, applications start writing their own numbers on the walls. Some stick. Some create conflicts.
Port 10004 is honest about what it is: a number with no official story. But it carries real traffic—patch management systems, device associations, developers debugging WordPress at 2am. The port itself doesn't care that IANA never blessed it. The Internet is using it anyway.
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