Port 10400 — Unassigned, Claimed by HomeSeer

The Range

Port 10400 falls in the registered port range (1024-49151).¹ These are ports that IANA makes available for assignment, but unlike the well-known system ports (0-1023), registered ports don't come with universal meaning. Your router manufacturer can assign them. Game studios can claim them. Home automation companies can build on them.

There's no official registration for port 10400 with IANA. It's a blank slate, waiting to be written on by whoever gets there first with a compelling use case.

The Unofficial Owner: HomeSeer

In practice, port 10400 belongs to HomeSeer, a home automation platform that dates back to the 1990s.² HomeSeer uses this port for its remote plugin API interface, a system that lets plugins run on separate machines and talk back to the main HomeSeer server.³

Here's what makes this architecture interesting: instead of running everything on one machine, you can distribute the load. A Z-Wave plugin runs on a Raspberry Pi in the basement. An automation engine runs on a NAS upstairs. They find each other through port 10400 and build a distributed network. The protocol speaks TCP. The connection is straightforward. The system works because everyone agrees where to meet.

How to Check What's Listening

If you suspect port 10400 is listening on your system, you can verify it:

On Linux or macOS:

sudo netstat -tuln | grep 10400
# or
sudo ss -tuln | grep 10400

On Windows:

netstat -ano | findstr :10400

This will tell you if anything is actually listening, and if it is, what process owns it.

Why Unassigned Ports Matter

The Internet's port system works because there are rules. IANA maintains the official registry. But the gaps—the unassigned ports—are where innovation happens. You can't run anything serious on port 53 (DNS) or port 443 (HTTPS) unless you own a massive infrastructure. But port 10400? You can build something there. Your home automation system can claim it. Your custom application can live there. Your organization can standardize on it.

The tension is real: IANA's registry prevents chaos. The unassigned gaps enable experimentation. Port 10400 is a quiet example of that balance in action. HomeSeer found this port, built something useful on top of it, and thousands of home automation setups now depend on it working. No formal assignment. No committee approval. Just pragmatism and adoption.

Related Ports

• Port 80 (HTTP) and Port 443 (HTTPS) — Web services that most systems understand
• Port 5353 (mDNS) — Local network service discovery, often used for finding devices like HomeSeer instances
• Port 8080, 8081 — Common alternate HTTP ports for administrative interfaces