Port 617 is a fossil. It was assigned to a service called sco-dtmgr (SCO Desktop Administration Server) in the 1990s, removed from the IANA registry in 2017, but it still shows up in port databases, network scans, and old documentation across the Internet. This is what happens when a port outlives the company that requested it.
What sco-dtmgr was
In the 1990s, the Santa Cruz Operation (SCO) was a major player in the Unix world. They sold SCO OpenServer and UnixWare—Unix-based operating systems that ran on x86 hardware and powered small businesses, corporate servers, and point-of-sale systems around the world.1
Port 617 was registered for sco-dtmgr, the SCO Desktop Administration Server. This was part of SCO's system administration toolset—a way for administrators to manage desktop systems remotely. The port was assigned for both TCP and UDP.2
At the time, this made sense. SCO had around 15,000 value-added resellers worldwide, and their Unix systems were everywhere.1 The Desktop Administration Server needed a port number, so Christopher Durham at SCO registered port 617 with IANA.
What happened to SCO
SCO sold its Unix assets to Caldera Systems in 2001. Caldera became The SCO Group, which spent the 2000s embroiled in legal battles over Unix intellectual property. The company went bankrupt in 2011. The rights to OpenServer and UnixWare were acquired by UnXis (later Xinuos), but the Desktop Administration Server was long gone by then.1
On May 18, 2017, IANA removed port 617 from the official service registry.3 The port assignment no longer exists. But the Internet doesn't forget.
Why port 617 still shows up
If you check a port database today, you'll still see port 617 listed as "sco-dtmgr." Network scanning tools like nmap still carry the entry. Security sites still reference it. Even though the service hasn't existed in decades and the registry entry was deleted in 2017, the assignment persists in cached databases and old documentation.
This is the nature of port assignments. They become part of the historical record. Once a port is associated with a service—especially in the well-known range (0-1023)—that association spreads across thousands of systems, databases, and configuration files. Even after the official assignment is removed, the ghost remains.
Other services that used port 617
Over the years, a few other services were documented using port 617:
- Mac OS X NetInfo: Apple's directory services system used port 617 for RPC-based communication in early versions of macOS4
- Arkeia backup software: Some sources mention port 617 being used by Arkeia, a commercial backup solution5
These were unofficial uses—software that happened to choose port 617, either because it was convenient or because they were running on systems where sco-dtmgr was already configured.
Security note
Because port 617 appears in old port databases and is no longer actively maintained, it has occasionally been flagged in security scans as potentially suspicious. Some sources note that Trojans have used port 617 in the past to communicate.6
This doesn't mean port 617 is inherently dangerous. It means that an abandoned, rarely-used port can be attractive to malware looking for a quiet place to operate. If you see traffic on port 617 on a modern network, it's worth investigating—not because the port itself is malicious, but because nobody should be running SCO Desktop Administration in 2026.
How to check what's listening on port 617
On Linux or macOS:
On Windows:
If something is listening on port 617 on your system and you're not running legacy SCO Unix software, it's worth finding out what it is.
Why unassigned ports matter
Port 617 isn't truly unassigned—it's de-assigned. It was assigned, used, and then removed from the registry when the service became obsolete.
This is rare. Most port assignments are permanent. Once IANA assigns a port, it typically stays assigned forever, even if the service becomes obscure or unused. Port 617 is one of the few examples of a well-known port that was actively removed from the registry.
It's a reminder that the port number system isn't just a technical specification—it's a historical record. Every port tells a story about what the Internet needed at a particular moment in time. Port 617's story is: SCO needed a way to manage desktop systems remotely in the 1990s. They got a port. The company collapsed. The service disappeared. The port was removed. But the number remains, echoing through databases and documentation, a ghost of the Unix wars.
Frequently asked questions about port 617
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