What Port 1742 Is
Port 1742 is a registered port, assigned by IANA to a service called 3Com-nsd — a network service daemon that shipped with 3Com networking equipment.1
3Com was once one of the most important networking companies in the world. They made the gear that connected offices before Cisco dominated everything. They shipped networking cards, switches, routers, and the software to manage them. At some point, 3Com registered port 1742 for their network service daemon, and IANA recorded it.
Then 3Com was acquired. The company dissolved. The software stopped being maintained. And port 1742 became what it is today: officially spoken for, practically empty.
The Registered Port Range
Port 1742 sits in the registered ports range (1024-49151). This range works differently from the well-known ports below 1024.
Well-known ports (0-1023) require root privileges to bind on Unix systems. They're reserved for major protocols — HTTP, HTTPS, SSH, DNS. The operating system enforces their protection.
Registered ports don't have that protection. Any application can bind to them. IANA maintains a registry of assignments to prevent conflicts, but registration is voluntary and enforcement is non-existent. If you want to run something on port 1742, nothing stops you. The 3Com-nsd assignment is a historical record, not a lock on the door.2
What's Actually There
Nothing, in most cases.
3Com-nsd hasn't been deployed in any meaningful way for years. The software is effectively abandoned, the company is gone, and there are no current applications that claim this port by default.
The SANS Internet Storm Center tracks scanning activity on port 1742 and records ongoing probes — dozens per day from IPs around the world.3 This is normal for registered ports with ghost assignments. Automated scanners don't know that a port is empty. They scan systematically, looking for anything that responds, whether the service they're probing still exists or not.
How to Check What's on This Port
If you see traffic on port 1742 on your network, it's almost certainly one of three things: a port scanner doing reconnaissance, a misconfigured application that picked this port arbitrarily, or something proprietary that chose it precisely because it's unused.
To check what's listening:
On Linux/macOS:
On Windows:
If something shows up, the process ID will tell you what it is. If nothing shows up, the port is closed — which is the expected result.
Why Unassigned (or Ghost-Assigned) Ports Matter
The port system works because most software respects the registry. HTTP goes to 80. HTTPS goes to 443. SSH goes to 22. When every application picks its own port arbitrarily, nothing can find anything.
Ghost-assigned ports like 1742 reveal something about the limits of that system. IANA can record an assignment, but it can't ensure the assigned software survives. Ports outlive the services they were given to. The registration persists long after the software is gone, which means the port isn't truly available for new uses — but it isn't truly in use either.
It's a small bureaucratic ghost story, repeated thousands of times across the registered range.
Frequently Asked Questions
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