Port 724: Unassigned — The empty space in the well-known range

Port 724 is officially unassigned. According to IANA, ports 717-728 across both TCP and UDP have no designated service.¹

This isn't an oversight. It's intentional space.

What the Well-Known Range Means

Port 724 lives in the well-known ports range (0-1023), also called system ports. These are the most privileged addresses in the port system. On most operating systems, only root or system processes can bind to these ports.

Getting a port assigned in this range requires IETF Review—a rigorous process that ensures only truly fundamental Internet services occupy these numbers.² HTTP got port 80. HTTPS got port 443. SSH got port 22. These are protocols the Internet depends on.

Port 724 hasn't earned that status yet. And that's fine.

Why Unassigned Ports Matter

The port number space is finite. There are only 65,535 possible ports (0-65535). The well-known range is even smaller—just 1,024 slots for the most critical services.

Unassigned ports serve two purposes:

1. Future capacity — When someone invents a new fundamental protocol, there's room for it. The Internet of 1990 didn't need a port for HTTPS. The Internet of 2000 did. Having unassigned ports means the system can evolve.

2. Breathing room — Not every number needs to be filled. The gaps make the system legible. When ports cluster around certain numbers, it's easier to remember what lives where.

What Might Be Listening on Port 724

Just because IANA hasn't assigned port 724 doesn't mean nothing uses it. Applications can bind to any port they want—official assignment or not.

To see if something is listening on port 724 on your system:

On Linux/macOS:

sudo lsof -i :724
# or
sudo netstat -tuln | grep :724

On Windows:

netstat -ano | findstr :724

If something appears, it's either:

• Custom software you or your organization installed
• A service using the port unofficially
• Potentially malicious software (though port 724 has no known malware associations¹)

The IANA Registry

IANA maintains the official Service Name and Transport Protocol Port Number Registry—the master list of what port does what. It's how the Internet agrees that port 80 means HTTP and port 25 means SMTP.

Port 724's entry in that registry reads simply: "Unassigned."¹

That status could change. If a protocol emerges that's critical enough, it could claim port 724. But until then, this port remains empty—a small gap in the numbered fabric of the Internet, waiting for something worthy to fill it.

Related Ports

• Ports 717-728 — The surrounding range, all officially unassigned¹
• Port 512-1023 — The upper half of the well-known range, where many unassigned ports cluster
• Port 1024-49151 — The registered ports range, where assignment rules are less strict