Port 566 is officially assigned to StreetTalk, a directory service that was part of Banyan VINES—a network operating system that competed with Novell NetWare and Microsoft in the 1980s and early 1990s. The protocol is extinct. The port remains registered as a historical artifact.
What StreetTalk Was
StreetTalk was a globally distributed directory service—the part of Banyan VINES that let you find people and resources across networks. Before Active Directory, before LDAP became ubiquitous, StreetTalk was doing something genuinely innovative: allowing seamless resource-sharing across geographically separated networks with a hierarchical naming system.1
Every entry in StreetTalk took the form item@group@organization. You could find a printer in Tokyo from an office in New York, assuming both were part of the same VINES network. For global corporations in the late 1980s, this was revolutionary.2
Why Port 566 Still Exists
The Internet Assigned Numbers Authority (IANA) keeps port 566 registered to prevent conflicts. Even though virtually nobody runs Banyan VINES anymore (the last version shipped in 19971), changing port assignments breaks things.
Somewhere, possibly, an ancient corporate network is still running VINES. More likely, someone's legacy application assumes port 566 belongs to StreetTalk and would fail if something else claimed it. So the port sits reserved, like a tombstone marking where a protocol used to be.
What Range Port 566 Belongs To
Port 566 is in the well-known ports range (0–1023), which requires IANA assignment. These are the ports meant for standardized services that everyone agrees on. Getting a well-known port in the 1980s meant your protocol was considered important enough to reserve a number permanently.
StreetTalk got that designation. Then lost the market to Novell and Microsoft. The port number outlived the company.
How to Check What's Listening on Port 566
On Linux or macOS:
On Windows:
You will almost certainly find nothing. Port 566 sits unused on nearly every computer in the world.
Why This Matters
Port 566 is a reminder that the well-known ports range is full of ghosts. Protocols that seemed essential in 1985 are forgotten by 2025. But the port numbers remain, because changing them risks breaking something nobody realizes still exists.
Every unassigned or obsolete port is a piece of networking archaeology—evidence of what we thought the Internet would need, what technologies competed for dominance, what lost.
StreetTalk lost. Port 566 is what remains.
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