What Range This Port Belongs To
Port 3636 sits in the registered ports range (1024–49151). These ports aren't controlled by IANA the way well-known ports (0–1023) are — you don't need special OS privileges to open them — but organizations can formally register their service with IANA to stake a claim on a number.
That registration is what separates a registered port from a dynamic one. It's a name on a deed, not a lock on a door.
The Registered Service: SerVistaITSM
IANA's records show port 3636 assigned to SerVistaITSM, registered in November 2002.1 SerVistaITSM was an IT service management platform — the kind of software that tracked helpdesk tickets and asset inventories in the early 2000s enterprise world.
The product has no meaningful presence today. No active documentation, no community, no vendors still shipping it. The registration persists in IANA's registry because registrations don't expire — they simply accumulate, like old forwarding addresses.
Some port databases also list OpsCenter as an alternate service on 3636, though this attribution is poorly sourced and inconsistent across references.2
What You Actually Find Here
In practice: not much. The SANS Internet Storm Center shows scattered scanning activity on port 3636 — automated crawlers probing it as part of sweeps across port ranges, not because anything known and valuable lives there.3 No significant malware families are associated with this port. No CVEs target it specifically.
If you find something listening on port 3636 on your own machine, it's almost certainly a custom application, a development server, or software that picked the number because it happened to be free.
How to Check What's Listening
On Linux or macOS:
On Windows:
If something shows up, the process ID in the output will tell you which program it is.
Why This Port Exists at All
The registered port system was designed to prevent collisions — two applications accidentally choosing the same port and stepping on each other. It worked, mostly, for the software that actively used it. But it also left a long trail of registrations for products that no longer exist, companies that dissolved, and protocols that never shipped.
Port 3636 is one of thousands of registered-but-dormant ports. The number is reserved, the service is gone, and the space between 1024 and 49151 quietly absorbs it.
Frequently Asked Questions
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