Port 1820: mcagent — A Name Without a Story

What Port 1820 Is

Port 1820 sits in the registered ports range — 1024 through 49151 — the middle tier of the port number space. Well-known ports (0-1023) are reserved for foundational protocols: HTTP, SSH, DNS, SMTP. Dynamic ports (49152-65535) are handed out temporarily by operating systems for outbound connections. Registered ports are the middle ground: services that aren't foundational enough for the well-known range, but stable enough that someone wanted to claim a permanent home.

IANA, the organization that manages port assignments, lists port 1820 as assigned to a service named mcagent for both TCP and UDP. The assignee on record is Ryoichi Shinohara.

That's where the documentation ends.

What mcagent Is

Nobody seems to know — at least not publicly. There's no RFC. No open-source implementation. No product documentation that mentions port 1820 as a standard port. The IANA assignment is real, but whatever mcagent was intended to be, it never achieved enough adoption to generate a trail.

This happens. The registered ports range has thousands of entries, and not every registration became a product, a protocol, or a deployed service. Some were reserved speculatively. Some were assigned to internal tools that never shipped publicly. Some are genuinely in use — just quietly, inside corporate networks that don't write blog posts.

Port 1820 has also been observed in association with Genetec, a physical security and video surveillance platform, though this is an unofficial use rather than anything IANA assigned.

If You See Port 1820 Open

If something is listening on port 1820 on your machine or network, you put it there — or software you installed did. This port has no default system service on Linux, macOS, or Windows.

To check what's using it:

macOS / Linux:

# Show which process is listening on port 1820
sudo lsof -i :1820

# Or with netstat
sudo netstat -tlnp | grep 1820

# Or with ss (modern Linux)
sudo ss -tlnp | grep 1820

Windows:

# Show process using port 1820
netstat -ano | findstr :1820

# Then look up the PID
tasklist | findstr <PID>

If something unexpected shows up, investigate it. An unrecognized service on an obscure port is worth understanding.

Why Unassigned (and Ghost-Assigned) Ports Matter

The port number space is finite. There are 65,535 of them. IANA's job is to prevent two different services from claiming the same number and creating ambiguity — the same kind of confusion that would happen if two airlines both used gate B7 for different flights.

Port 1820's assignment exists as a record. Whether mcagent was ever deployed widely, whether it still runs somewhere, whether the assignment was a mistake — none of that is publicly documented. What's certain is that the port is reserved, and if you're running something on 1820, you're running it in a space that someone else once claimed.

Related Ports

Nearby ports with known services:

• Port 1812 — RADIUS authentication
• Port 1813 — RADIUS accounting
• Port 1883 — MQTT (IoT messaging)