What Runs Here
Port 627 is officially assigned to "PassGo Tivoli" for both TCP and UDP.1 The problem? Nobody knows what PassGo Tivoli actually was.
No RFC. No technical documentation. No surviving product information. Just a name in the IANA registry that points to software that appears to have vanished completely from the Internet's memory.
The Mystery of PassGo
The name suggests a connection to Tivoli Systems, the Austin-based company founded in 1989 that built enterprise management software. IBM acquired Tivoli for over $750 million in 1996.2 But searching for "PassGo" in connection with Tivoli yields nothing. No product announcements. No user manuals. No technical specifications.
The most likely explanation: PassGo was an early Tivoli product or component that died quietly—either discontinued, renamed, or absorbed into other software. The company moved on. The software disappeared. But the port registration remained, frozen in the IANA database like a fossil.
Why This Port Matters
Port 627 represents something important about how the Internet works: official assignments are forever.
When IANA assigns a port number to a service, that assignment doesn't expire when the software dies. There's no mechanism for reclaiming abandoned ports. The registry just grows, accumulating the names of dead protocols and forgotten services.
This creates a strange situation. Port 627 is officially "taken"—you're not supposed to use it for your own service. But the service it's assigned to probably hasn't existed in 25 years. The port sits empty, reserved for a ghost.
What the Well-Known Range Means
Port 627 falls in the well-known port range (0-1023), which requires root privileges to bind on Unix systems. These ports were meant for standard, widely-used services. IANA tightly controlled assignments in this range.
But "well-known" doesn't mean "actually used." Many ports in this range are registered to services nobody remembers. The range is full of ghosts like PassGo Tivoli—officially assigned, practically abandoned.
How to Check What's Listening
Even though PassGo Tivoli is almost certainly defunct, something could be listening on port 627 on your system. Here's how to check:
On Linux or macOS:
On Windows:
If nothing appears, the port is closed. If you see output, something is using it—though it's almost certainly not PassGo Tivoli.
The IANA Registry as Graveyard
The Internet Assigned Numbers Authority maintains the official port registry.3 It's a remarkable document—a complete history of network services going back decades. But it's also a graveyard.
Hundreds of ports are assigned to services that no longer exist. Protocols designed for hardware that was scrapped in the 1990s. Software built by companies that went bankrupt or were acquired and dismantled. Names that meant something to someone, somewhere, but now mean nothing to anyone.
Port 627 is one of these. Officially registered. Technically unavailable. Practically meaningless.
This is the Internet's long memory. Nothing is truly deleted. Assignments made thirty years ago persist in the registry, preserved not because they're useful, but because there's no mechanism to remove them.
Frequently Asked Questions About Port 627
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