Port 764 is officially assigned to a service called "omserv," but if you try to find out what omserv actually does, you'll hit a wall. There's a name in the registry, but no documentation, no active use, and no clear history. It's one of those ports that exists on paper but nowhere else.
What We Know (And Don't Know)
Port 764 appears in IANA's Service Name and Transport Protocol Port Number Registry1 with the designation "omserv" for both TCP and UDP. The assignment dates back to at least RFC 17002 from October 1994, which documented port assignments that existed even earlier.
But that's where the trail goes cold.
RFC 1700 lists the port with no description. No contact person. No reference document. Just:
The Well-Known Ports Range
Port 764 falls in the well-known ports range (0-1023), also called System Ports. These are assigned by IANA through formal IETF Review or IESG Approval procedures3—meaning someone, at some point, made an official request for this port number.
But who? And for what? The documentation doesn't say.
Well-known ports are typically reserved for foundational Internet services—protocols that need consistent port numbers across all systems. HTTP on port 80. HTTPS on port 443. SSH on port 22. These are services everyone needs to find in the same place.
Port 764 was given that same level of privilege. But unlike those services, omserv never became part of the Internet's visible infrastructure.
The Mystery of omserv
The name "omserv" suggests "object manager service" or something similar, but that's speculation. A 2003 mailing list post4 shows someone finding port 764 open on their Red Hat Linux firewall with no associated process running—the port accepted connections but never responded. They asked what omserv was. The archive shows follow-up messages exist, but their contents aren't preserved.
That might be the entire documented history of someone encountering this service in the wild.
There's no RFC defining an omserv protocol. No vendor documentation. No open-source implementation preserved in code repositories. The service either never launched, operated so briefly that all traces vanished, or ran on proprietary systems whose documentation was never published.
Why Unassigned (and Ghost) Ports Matter
Port 764 isn't technically unassigned—it has an assignment. But functionally, it might as well be. This happens more often than you'd think. The IANA registry contains hundreds of ports with names but no active services, relics of protocols that died or were never born.
These ghost ports matter because:
- They're reserved — You can't officially use port 764 for a new service without potentially conflicting with whatever omserv was supposed to be
- They show up in scans — Security tools flag well-known ports, so seeing 764 open raises questions even though nobody knows what should be there
- They're archaeological sites — Each one represents a moment in Internet history, a decision someone made, a protocol someone designed
The registry preserves these assignments not because the services are active, but because port numbers are never truly freed. Once assigned, they carry that designation forward, just in case the service ever returns—or just in case someone, somewhere, is still using it.
How to Check What's on Port 764
If you find port 764 open on a system, here's how to investigate:
On Linux/macOS:
On Windows:
If something is listening on port 764, it's almost certainly not the original omserv—it's either a modern application that happened to choose this port, malware using an obscure port to hide, or a misconfiguretd service.
The Honest Truth
Port 764 is assigned to omserv. But omserv is a name without a protocol, a reservation without a service, a decision preserved in the registry with all context lost.
It's one of the Internet's small mysteries—not important enough to investigate deeply, but strange enough to make you wonder what was supposed to be here, and why it never arrived.
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