Port 301: Unassigned — A Reserved Space in the Well-Known Range

Port 301 is unassigned. It has no official service, no RFC defining its purpose, no protocol that calls it home. It sits in the well-known ports range (0-1023)—the most restricted, carefully guarded addresses in the Internet's numbering system—but nothing has ever claimed it.¹

What Range This Port Belongs To

Port 301 is in the well-known ports range (0-1023), also called system ports. These ports are controlled by the Internet Assigned Numbers Authority (IANA) and require "IETF Review" or "IESG Approval" to be assigned.²

This is the prestigious range. Port 22 (SSH) is here. Port 80 (HTTP) is here. Port 443 (HTTPS) is here. These are the ports that define how the Internet works.

But port 301 is empty. Unassigned. Available.

Why Ports Remain Unassigned

Approximately 24% of the well-known ports range remains unassigned.² This isn't neglect—it's strategy.

IANA doesn't hand out well-known ports casually. They're reserved for protocols that matter, protocols that will be deployed widely enough to justify occupying a permanent address in the Internet's core infrastructure.

When a port is de-assigned (perhaps because a protocol became obsolete), IANA includes a comment in the registry noting its historic usage. The port isn't immediately reused—it returns to the unassigned pool and waits until all other unassigned ports in the range have been assigned first.³

Port 301 appears to have never been assigned. It's not a retired address. It's space held in reserve.

Port Number States

Every port exists in one of three states:⁴

• Assigned: Currently assigned to a service listed in the IANA registry
• Unassigned: Available for assignment upon request (this is port 301)
• Reserved: Not available for regular assignment; held by IANA for special purposes (like port 0 or boundary values)

Unassigned ports aren't typically listed explicitly in the registry—they're the gaps between assigned services.

Unofficial Uses

Because port 301 is unassigned, applications are technically free to use it for custom purposes. There are no widely documented unofficial uses of port 301, but any private system could theoretically run a service on this port without conflicting with a standard protocol.⁵

If you find something listening on port 301 on your network, it's a custom application—not a standard Internet service.

How to Check What's Listening

On Unix-like systems (Linux, macOS):

# Check if anything is listening on port 301
sudo lsof -i :301

# Or use netstat
sudo netstat -tulpn | grep :301

# Or use ss (modern replacement for netstat)
sudo ss -tulpn | grep :301

On Windows:

netstat -ano | findstr :301

If nothing returns, the port is closed—no service is listening.

Why Unassigned Ports Matter

The unassigned ports in the well-known range are part of the Internet's future. They represent room to grow, space for new protocols we haven't invented yet, addresses for problems we haven't encountered.

Port 301 might remain empty forever. Or it might one day carry the next fundamental protocol of the Internet.

For now, it's a door with no service behind it. Just an address. Waiting.