Port 811 — Unassigned

Status: Unassigned
Range: Well-Known Ports (0-1023)
Protocols: TCP/UDP
IANA Assignment: None

Port 811 is officially unassigned. It belongs to the well-known ports range—the first 1,024 port numbers (0-1023) that IANA controls and allocates for standardized services. But port 811, along with ports 812-827, has never been claimed.¹

What "Unassigned" Means

The well-known ports range is supposed to be the Internet's most valuable real estate. These are the ports everyone knows: 80 for HTTP, 443 for HTTPS, 22 for SSH. They're standardized so that when you connect to a web server, you don't have to guess which port it's listening on.

But not every number in that range has a tenant.

Port 811 is unassigned, meaning:

• No official service is registered to use it — IANA has never allocated this port to any protocol or application
• It's available for assignment — If someone develops a protocol that needs a well-known port, they can apply to IANA to claim 811
• It might be used informally — Just because IANA hasn't assigned it doesn't mean nothing is listening there on your network

Why Unassigned Ports Exist

You might think every port in the well-known range would be spoken for by now. But the Internet grew unevenly. Some numbers were assigned in the 1980s to services that never caught on. Others were reserved and then abandoned. And some, like 811, were simply never needed.

The well-known ports range is full of these gaps—numbers held in reserve for a future that may never come. They're addresses on streets where no one lives.

Checking What's On Port 811

Even though IANA hasn't assigned port 811 to anything, that doesn't mean nothing is using it. Applications can listen on any port. Malware sometimes squats on unassigned ports precisely because they're not monitored as closely.

To see what's listening on port 811 on your system:

Linux/macOS:

sudo lsof -i :811
sudo netstat -tulpn | grep :811

Windows:

netstat -ano | findstr :811

If something is listening on port 811 and you don't recognize it, investigate. Legitimate software rarely uses unassigned well-known ports.

The Well-Known Ports Range

Port 811 belongs to the System Ports or Well-Known Ports range (0-1023). These ports are:

• Controlled by IANA — You can't just start using them for your application; they require official assignment
• Often require root/administrator privileges — On Unix-like systems, only privileged processes can bind to ports below 1024
• Meant for standardized services — The whole point is that everyone agrees on what each port means

The other ranges are:

• Registered Ports (1024-49151) — Assigned by IANA but less strictly controlled
• Dynamic/Private Ports (49152-65535) — Not assigned; free for temporary use by any application

Related Ports

Port 811 sits in a cluster of unassigned ports:

• 811-827 — All unassigned as a group¹

Nearby assigned ports:

• 800/TCP — mdbe-daemon (unrelated to 811)
• 828/TCP-UDP — itm-mcell-s (where assignments resume)