Port 579 is officially assigned to decbsrv—Digital Equipment Corporation's batch server service. Both TCP and UDP versions are registered with IANA.1
The assignment is real. The service is dead.
What DEC Was
Digital Equipment Corporation dominated enterprise computing in the 1970s and 1980s. Their VAX systems ran universities, hospitals, and research labs. Their DECserver terminal servers connected hundreds of serial terminals to mainframes over Ethernet.2
When DEC needed a port for batch job processing between servers, they registered port 579. IANA assigned it. The protocol went into production.
Then DEC collapsed. Compaq absorbed them in 1998. HP absorbed Compaq in 2002. The original DEC technology was sold off in pieces, discontinued, or replaced entirely.
Port 579 remained in the registry.
What This Port Teaches
The IANA port registry isn't just a technical database—it's an archaeological record. Every abandoned port represents:
- A company that no longer exists
- A protocol that lost to a competitor
- A solution to a problem nobody has anymore
- Infrastructure that was critical until it wasn't
Port 579 sits in the well-known range (0-1023), reserved for services deemed important enough to merit global coordination. It seemed important in 1985. By 2000, it was obsolete.
Security Implications
Some security databases flag port 579 as potentially associated with trojans.3 This isn't because the original DEC service was malicious—it's because abandoned ports make excellent hiding places.
When a port has an official assignment but no legitimate software actually uses it, malware authors notice. An unexpected connection on port 579 isn't DECserver traffic—it's something pretending to be something that nobody remembers.
Checking What's Listening
On Linux or macOS:
On Windows:
If something is listening on port 579, it's not Digital Equipment Corporation. DEC has been gone for over two decades.
Why Unassigned Ports Matter
Paradoxically, port 579 isn't unassigned—it's assigned to nothing that exists. This is arguably worse.
Truly unassigned ports in the well-known range (0-1023) can be reassigned if someone builds something important enough. But port 579 is technically taken. The registration exists. The company doesn't.
IANA rarely revokes port assignments. The registry grows but almost never shrinks. Every failed company, every abandoned protocol, every obsolete service leaves a permanent shadow in the port number space.
The Well-Known Range
Port 579 sits in the well-known port range (0-1023), which requires root/administrator privileges to bind to on Unix-like systems. This was a security measure: if binding to these ports requires elevated privileges, then services running on them must have been started by a trusted administrator.
But that logic assumes the registered services still exist. When port 579's legitimate service disappeared, the security model didn't account for it. The port requires privileges to use, but there's nothing legitimate left to use it for.
Related Ports
Other DEC-assigned ports from the same era:
- Port 567: DSTmail (another dead DEC protocol)
- Port 568: DEC Fibre Link Protocol
- Port 577: vettcp (DEC VT over TCP)
Most are similarly extinct. The IANA registry preserves them like insects in amber—visible, documented, but no longer alive.
The Ghost Ports
The Internet has thousands of ports like 579. Officially assigned. Technically registered. Practically extinct.
They're ghosts—visible in the registry, queryable in databases, but untethered from any living system. Port 579 will likely remain assigned to decbsrv forever, a permanent memorial to a company that shaped computing history before vanishing entirely.
Every packet that accidentally arrives at port 579 is looking for something that no longer exists.
Frequently Asked Questions About Port 579
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