Port 266: Unassigned — An Empty Door in the Well-Known Range

Port 266 is unassigned. Both TCP and UDP on this port have no official service designation from IANA (Internet Assigned Numbers Authority).¹

This is stranger than it sounds.

The Well-Known Range

Port 266 sits in the well-known ports range (0-1023). These are the System Ports, the prestigious addresses reserved for fundamental Internet services. SSH lives at 22. HTTP at 80. HTTPS at 443. These ports require superuser privileges to bind on Unix-like systems because they're supposed to be important.

But port 266? Nobody home.

What This Means

The well-known range was created to provide a stable, universally recognized set of port numbers for essential Internet services. Port 266 was reserved as part of this range but never assigned to a protocol. It's been officially listed as "Unassigned" in the IANA registry since at least 2006.¹

It could be assigned someday. Someone could submit a formal request to IANA with a protocol specification, a use case, and documentation. But for now, it's empty.

Unofficial Use

Unlike some unassigned ports that get claimed by popular applications anyway, port 266 doesn't appear to have any widespread unofficial use. No major software has colonized this space. No protocol has claimed squatter's rights.

It's genuinely dormant.

Occasionally, proprietary applications might use port 266 for internal purposes, but there's no documented pattern of this.² When port scanners sweep through a network, they rarely find anything listening here.

Why Unassigned Ports Matter

The existence of unassigned ports in the well-known range reveals something about how the Internet was designed: with optimism about growth. The architects reserved space for services that didn't exist yet, protocols that hadn't been invented, needs that hadn't emerged.

Some of that reserved space got filled. Some of it, like port 266, is still waiting.

These empty addresses also serve a practical function. They're available for new protocols that truly need a well-known port. The bar is high—you need IANA approval, proper documentation, a real use case—but the space exists.

How to Check This Port

On Linux or macOS, check what's listening on port 266:

# Check TCP port 266
lsof -i TCP:266

# Check UDP port 266
lsof -i UDP:266

# Or use netstat
netstat -an | grep 266

On Windows:

netstat -an | findstr :266

Most likely, you'll find nothing. Port 266 is typically silent.

The Architecture of Empty Space

Port 266 is a reserved seat at a table where no guest has arrived. It's part of the Internet's formal structure, documented in official registries, protected by operating system privileges, but unused.

There's something beautiful about that. The Internet has room for services that don't exist yet. Port 266 is one of those rooms, door closed, lights off, waiting.