Port 759 sits in the well-known ports range with an official IANA assignment, but its story is one of obsolescence. Officially labeled "con" (connection), its actual purpose was serving Mac OS X's NetInfo directory service—a system that no longer exists.
What Ran on Port 759
Port 759 (both TCP and UDP) was assigned to "con" in IANA's registry.1 But in practice, this port was part of the RPC-based infrastructure used by NetInfo on Mac OS X systems.2
NetInfo was a hierarchical distributed database that stored administrative data on Mac OS X Server and earlier NeXTSTEP systems. It tracked:3
- User and group accounts
- Email configurations
- Network filesystem (NFS) mounts
- Printer configurations
- Computer resources and network settings
Port 759 was one of several ports (600-1023) used by Mac OS X's RPC service layer (ipcserver) to support NetInfo communication.4
What Happened to NetInfo
NetInfo is dead. Apple removed it completely in Mac OS X 10.5 Leopard (2007).5 Its functionality was replaced by Open Directory, which had been part of Mac OS X Server since version 10.1 or 10.2 and became the sole directory service going forward.
This means port 759's primary real-world purpose disappeared nearly two decades ago. The port remains in IANA's registry with its "con" assignment, but that assignment never had widespread adoption outside of Apple's ecosystem—and Apple abandoned it.
What Port 759 Means Today
Port 759 is effectively unused. You're unlikely to find any modern service listening on it. It exists in the well-known range (0-1023), which means:
- It requires root/administrator privileges to bind to on Unix-like systems
- It's permanently assigned by IANA (even if the assignment is obsolete)
- It won't be reassigned to another service
Checking What's Listening
On Linux or macOS:
On Windows:
If you find something listening on port 759, it's either legacy Mac OS X infrastructure (on very old systems) or something unofficial using an abandoned port.
Why Unassigned and Obsolete Ports Matter
Port 759 demonstrates an important reality about the port system: not every assignment ages well. Technologies evolve. Companies abandon protocols. Services get replaced.
The well-known ports range (0-1023) contains hundreds of assignments. Some carry the entire Internet (like port 443 for HTTPS). Others, like port 759, are archaeological artifacts—officially assigned but functionally extinct.
These ghost ports serve as a reminder that the Internet is built on layers of history. Every obsolete port was once someone's solution to a real problem. NetInfo solved directory services for Mac OS X Server. It worked until something better came along.
Port 759 carried the administrative heartbeat of early Mac OS X servers—user accounts, network filesystems, printer configurations—until Apple deleted the entire system and never looked back. The port remains, but the purpose is gone.
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