Port 287: K-BLOCK — The Ghost in the Registry

Port 287 sits in the well-known ports range (0-1023), officially assigned by the Internet Assigned Numbers Authority to a protocol called "K-BLOCK."¹ That's all we know. No RFC describes it. No documentation explains what it does. No one remembers using it.

What We Know

Service Name: K-BLOCK
Transport Protocols: TCP and UDP
Registrant: Simon P. Jackson
Port Range: Well-known ports (0-1023)
Documentation: None found

The IANA registry lists port 287 as assigned to both TCP and UDP for K-BLOCK, with Simon P. Jackson as the contact.¹ That single line in the registry is the only evidence this protocol was ever intended to exist.

What Range This Port Belongs To

Port 287 falls within the well-known ports range (0-1023). These are the ports reserved by IANA for system services and widely-used protocols. Getting a number in this range meant something in the early Internet—it signaled that your protocol was important enough to deserve a permanent, globally-recognized address.

Ports in this range require special privileges to bind to on Unix-like systems. They're meant for fundamental Internet services: HTTP on 80, SSH on 22, DNS on 53. Port 287 was granted this status for K-BLOCK, but whatever K-BLOCK was supposed to be, it never became fundamental to anything.

The Mystery of K-BLOCK

No RFC describes K-BLOCK. No technical documentation explains its purpose. No mailing list archives discuss its implementation. Simon P. Jackson's name appears in the IANA registry and nowhere else in the technical literature we can find.

This is unusual. Most protocols assigned well-known ports have RFCs, documentation, implementation guides. Even failed protocols leave paper trails—draft specifications, conference presentations, someone's abandoned GitHub repository. K-BLOCK has none of this.

Three possibilities:

1. K-BLOCK was planned but never implemented
2. K-BLOCK was implemented but never deployed beyond a single organization
3. K-BLOCK existed briefly and was abandoned before anyone documented it

We don't know which. The registry entry is a gravestone with no epitaph.

Why Unassigned Ports Matter

Technically, port 287 isn't unassigned—it's assigned to K-BLOCK. But functionally, it might as well be unassigned. No known software listens on this port by default. No firewall rules specifically target it. No security scanners warn about it.

This matters because the Internet's port numbering system is finite. There are only 1,024 well-known ports, and IANA assigned one of them to a protocol that appears never to have existed in any meaningful way. It's like reserving a parking space for a car that never arrives.

The well-known ports range is mostly full now. Modern protocols fight for registered ports (1024-49151) or settle for dynamic ports (49152-65535). But port 287 sits empty in the premium range, holding space for a ghost.

Checking What's Listening

On Unix-like systems, check if anything is listening on port 287:

# Check if port 287 is in use
sudo lsof -i :287

# Or with netstat
sudo netstat -tulpn | grep :287

# Or with ss
sudo ss -tulpn | grep :287

On Windows:

# Check if port 287 is in use
netstat -ano | findstr :287

If you find something listening on port 287, it's not K-BLOCK—it's something else using an effectively abandoned number. Maybe custom software within an organization. Maybe malware that chose an obscure port. But not K-BLOCK.

The Ports That Time Forgot

Port 287 isn't alone. The IANA registry contains dozens of assigned ports with no documentation, no RFCs, no living software that uses them. They're archaeological artifacts from the early Internet—ideas someone had, numbers someone requested, protocols that never materialized or disappeared without record.

They remind us that the Internet's infrastructure isn't just the protocols that succeeded. It's also the ones that failed, the ones that were planned but never built, the ones whose creators moved on to other things and never looked back.

Port 287 is a number waiting for a protocol that may never come.