Port 383 sits in the well-known range (0-1023) but has no official IANA assignment. It was claimed by HP OpenView Network Node Manager for the Performance Data Alarm Manager service—software that monitored network performance and managed alarms when things went wrong.1
HP OpenView is dead now. The product line was discontinued years ago. But port 383 remains, flagged in security databases and vulnerability scanners as a port that once carried exploits.2
What HP OpenView Did
HP OpenView was enterprise network management software for large organizations. It collected performance data from network devices, analyzed it, and raised alarms when metrics went out of bounds. Port 383 specifically handled the alarm management component—receiving performance data and triggering notifications.3
The service ran on both TCP and UDP port 383, depending on whether connection reliability was needed or speed mattered more.
The Security Problem
Port 383 became known for an arbitrary file deletion vulnerability. Attackers who found it open could exploit the HP OpenView service to delete files on the target system.4 This wasn't theoretical—it happened enough that port 383 earned a permanent spot in security scanning tools.
Since the software is discontinued, there's no reason for this port to be open on modern systems. If you find it listening, something is either very old or pretending to be HP OpenView.
What Well-Known But Unassigned Means
Ports 0-1023 are the well-known range, reserved for services assigned by IANA. But not every port in this range has an assignment. Port 383 is one of the gaps—it was used by commercial software without going through the official assignment process.
This happens. Companies build products, pick a port number that seems free, ship the software. If the product succeeds and becomes widespread, the port association sticks in documentation and network configs. If the product dies, the port becomes a historical artifact.
Checking What's Listening
On Linux or macOS:
On Windows:
If something is listening on port 383, investigate what it is. It shouldn't be HP OpenView (that's ancient). It might be legitimate software that reused the port number, or it might be something pretending to be legitimate.
Why Unassigned Ports Matter
The gap between official assignments and actual usage is where confusion lives. Port 383 shows up in documentation as "HP Data Alarm Manager" even though IANA never assigned it. Security scanners flag it. Network admins block it. All for software that no longer exists.
These ghost ports are part of the Internet's memory. They're evidence that the port number space isn't just a clean registry—it's an archaeological site with layers of discontinued products, abandoned protocols, and decisions made decades ago that still echo in firewall rules.
Port 383 carried enterprise monitoring traffic. Now it carries nothing but warnings.
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