Port 828 is officially assigned to itm-mcell-s, a service that was used by NetInfo on Mac OS X. Both TCP and UDP protocols can operate on this port, though you're unlikely to see either in use today.
What Ran Here
NetInfo was a hierarchical distributed database that shipped with NeXTSTEP and early Mac OS X systems. It stored administrative data—user accounts, group permissions, email configurations, NFS mounts, printer settings, network resources. Think of it as a directory service that predated Active Directory on Windows and Open Directory on modern macOS.1
Port 828 was one of several ports (ranging from 600-1023) reserved for Mac OS X RPC-based services that NetInfo relied on to communicate across the network.2
What Happened to It
Apple removed NetInfo entirely in Mac OS X 10.5 Leopard (released in 2007), replacing it with Open Directory—which had actually been part of Mac OS X Server since versions 10.1 or 10.2.3 The transition was complete. NetInfo was gone.
But port 828 remains in the IANA registry, officially assigned to itm-mcell-s—a service that no longer exists in any modern operating system.4
The Well-Known Range
Port 828 sits in the well-known ports range (0-1023). These ports are assigned by IANA and typically reserved for established, widely-used services. HTTP uses port 80. HTTPS uses port 443. SSH uses port 22.
Port 828 was assigned for a service that was genuinely important—at the time. The well-known range doesn't guarantee eternal relevance. It just means someone thought this service mattered enough to reserve a spot in the most protected part of the port system.
Security Note
Because port 828 is rarely used today, security databases have occasionally flagged it when malware attempts to use abandoned ports for communication.5 This doesn't mean the port itself is dangerous—it means attackers sometimes exploit the fact that nobody's watching it.
If you see unexpected traffic on port 828, investigate it. Legacy Mac systems in very old environments might still have NetInfo running, but that's increasingly unlikely. Modern traffic on this port is worth questioning.
Checking What's Listening
On Linux or macOS:
On Windows:
If nothing returns, nothing's listening. That's the expected state for most systems in 2026.
Why Unassigned Ports Matter
Wait—this port isn't unassigned. It's assigned to itm-mcell-s. But functionally, it behaves like an unassigned port because the service it was built for is extinct.
This matters because the port system is full of these ghosts. Services get deprecated. Protocols get replaced. Companies go out of business. But the port assignments remain, frozen in the IANA registry, holding space for services that will never return.
The well-known range (0-1023) contains the history of the Internet. Some ports still carry the traffic they were designed for. Others, like 828, are monuments to ideas that didn't survive.
Related Ports
- Port 111 — Portmapper/RPCbind, another RPC service (still in use)
- Port 757 — Another Mac OS X RPC-based service used by NetInfo6
- Port 389 — LDAP, which replaced NetInfo's directory service functionality
Frequently Asked Questions
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