What Port 1788 Is
Port 1788 falls in the registered port range (1024–49151). These ports are managed by IANA, which maintains a registry of service names so that different applications don't accidentally collide on the same port number.
IANA lists port 1788 as assigned to a service called psmond on both TCP and UDP.1
That's where the official story ends.
The psmond Mystery
"psmond" is almost certainly short for "process monitor daemon" — a background service that watches running processes and reports system metrics. A few unrelated open-source projects have used that name over the years, including a Python tool that ships data to Elasticsearch2 and a Rust tool that flags high CPU and memory consumers.3
Neither is the psmond that IANA registered. There is no RFC defining the protocol. No specification describing what psmond sends or how it handshakes. No documentation about who registered the name or when. The IANA entry exists as a placeholder for something that, as far as anyone can tell, never became a real deployed protocol.
This is more common than you'd think. The registered port range contains thousands of names — services registered by companies or developers in anticipation of a product that was never released, or was released without ever spreading, or quietly died. The IANA entry remains. The service doesn't.
What You'll Actually Find on Port 1788
If you see traffic on port 1788 in the wild, it's almost certainly one of two things:
A custom application. Developers sometimes pick unoccupied registered ports for internal tools, game servers, or proprietary protocols. There's nothing wrong with this — the registered range exists partly so that applications can find a named home if they want one.
Scanning activity. Automated scanners sweep broad port ranges looking for anything that responds. Port 1788 shows up in scan logs at the SANS Internet Storm Center4 — not because it's a known target, but because scanners don't skip it.
How to Check What's Using Port 1788
If port 1788 is open on your system and you want to know why:
On Linux or macOS:
On Windows:
The process ID in the output will tell you exactly what's listening. Look it up in your task manager or with ps aux | grep <pid> on Unix systems.
Why Unassigned Ports Matter
The registered range exists as a coordination layer. When a new protocol needs a home, its creators register a port with IANA so that other protocols don't accidentally claim the same number. The alternative — everyone picking ports at random — leads to conflicts, confusion, and security headaches.
Port 1788's registration, even for a service that never materialized, is that coordination layer doing its job. The port is spoken for. Other protocols know not to use it. If psmond ever arrives in earnest, it has a reserved space waiting.
Until then, 1788 is an empty room with a nameplate on the door.
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