Port 940: Unassigned — A quiet space in the well-known range

Port 940 sits in the well-known port range (0-1023), but unlike its famous neighbors like DNS (53) or HTTPS (443), it has no official assignment. IANA—the organization responsible for port assignments—lists it as part of the unassigned range 916-952.¹

What "Unassigned" Means

Ports can exist in several states:

Assigned — A protocol or service officially uses this port (like SSH on 22 or SMTP on 25)

Reserved — IANA holds the port for special purposes and doesn't assign it

Unassigned — Available for assignment if someone requests it for a new protocol

Port 940 is unassigned. It's available. Nobody has claimed it because nobody has needed it badly enough to go through the formal assignment process.

The Well-Known Range

The well-known port range (0-1023) is supposed to be the prestigious neighborhood—ports here require IANA assignment and typically need root/administrator privileges to bind to on Unix-like systems. These are the ports where foundational Internet protocols live.

But even in this exclusive range, there are gaps. The 916-952 block is one of them—37 consecutive ports sitting empty while the Internet runs around them.

Port 940 is right in the middle of that silence.

No Known Unofficial Use

Some unassigned ports develop informal uses—applications that pick a number and use it without formal blessing. Port 940 hasn't even achieved that distinction. Security databases show no trojans, no malware, no unofficial services commonly associated with this port.¹

It's genuinely quiet.

Why Unassigned Ports Matter

The existence of unassigned ports in the well-known range represents capacity for the future. If a new foundational protocol emerges—something as essential as HTTP or DNS once was—there are still port numbers available in the range where system-level services traditionally live.

Port 940 is one of those options. Waiting.

How to Check What's Listening

Even though port 940 has no official assignment, something on your system might still be using it. Here's how to check:

Linux/macOS:

# Check if anything is listening on port 940
sudo lsof -i :940

# Or using netstat
sudo netstat -tulpn | grep :940

# Or using ss (modern replacement for netstat)
sudo ss -tulpn | grep :940

Windows:

# Check port 940
netstat -ano | findstr :940

If you see output, something is using port 940 locally—either a legitimate application or something worth investigating.

The Bureaucracy of Port Assignment

Getting a port officially assigned by IANA involves submitting a formal request, justifying why your protocol needs it, and going through a review process defined in RFC 6335.² For well-known ports (0-1023), the bar is particularly high—you need to demonstrate that your service is fundamental enough to deserve space in this restricted range.

Port 940 hasn't met anyone who cleared that bar yet.

The Bigger Picture

In the complete port number space (0-65535), the well-known range is tiny—less than 2% of available port numbers. Most services don't need a well-known port. They use registered ports (1024-49151) or ephemeral ports (49152-65535) and work just fine.

But for historical and operational reasons, some services need to be findable at predictable, low-numbered ports that require privilege to use. That's what the well-known range provides.

Port 940 is one of the reserve slots. Available for the next protocol that truly needs it.