What Runs on Port 757
Port 757 is officially assigned to ipcserver, a service used by NetInfo—Apple's RPC-based directory service for managing users, groups, printers, and network configuration data.1 The service operates on both TCP and UDP protocols.
Here's the catch: NetInfo hasn't existed for almost two decades.
The NetInfo Story
NetInfo was born in NeXTSTEP, the operating system created by Steve Jobs' company NeXT in the late 1980s. When Apple acquired NeXT in 1997 and used its technology as the foundation for Mac OS X, NetInfo came along for the ride.2
From Mac OS X 10.0 through 10.4 Tiger, NetInfo served as the primary mechanism for managing local user accounts, groups, and system configuration. It stored everything in a hierarchical distributed database—a binary format that could be shared across networks.3
But Apple had been planning NetInfo's retirement since Mac OS X 10.2 Jaguar, gradually shifting toward Open Directory, a standards-based alternative built on LDAP (Lightweight Directory Access Protocol).4
In 2007, with the release of Mac OS X 10.5 Leopard, NetInfo didn't just get deprecated—it was completely removed. Not hidden, not relegated to advanced users. Gone.5 Apple replaced it with a local search node called dslocal that uses standard property list files instead of NetInfo's proprietary database format.
Why Port 757 Still Exists
Port 757 sits in the well-known range (0-1023), assigned by IANA through formal review processes. These assignments are rarely revoked, even when the service disappears completely.
So port 757 remains on the official registry, pointing to a service that was removed from its only major implementation almost 20 years ago. It's a fossil—evidence of technology that mattered once and vanished.
What Actually Uses Port 757 Today
Effectively nothing.
Unless you're running an extremely old Mac OS X system (10.4 Tiger or earlier), you won't encounter NetInfo or port 757 in active use. Modern macOS systems don't include NetInfo at all.
Checking If Anything Is Listening
You can verify nothing is using port 757 on your system:
On macOS/Linux:
On Windows:
If nothing returns, the port is unused—which is exactly what you should expect on any modern system.
Why Unassigned and Abandoned Ports Matter
Ports like 757 tell the history of the Internet's nervous system. Every port number in the well-known range represents a decision someone made about what services deserved permanent addresses in the 0-1023 space.
Some of those decisions aged well (port 22 for SSH, port 443 for HTTPS). Others, like port 757, mark technologies that solved real problems for a time and then were replaced by better solutions.
The port numbers remain because the registry is meant to be stable. Removing assignments creates the risk of conflicts if someone reuses the number for something else. So port 757 stays registered to NetInfo, a service that no longer exists, on the chance that somewhere, someone is still running Mac OS X 10.4 Tiger and needs NetInfo to work.
That's probably nobody. But the port assignment remains, just in case.
Related Ports
- Port 389 — LDAP, the technology that replaced NetInfo in Open Directory
- Port 636 — LDAPS (LDAP over SSL/TLS), secure directory services
- Port 464 — Kerberos Change/Set password, used by modern macOS authentication
Frequently Asked Questions About Port 757
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