Port 660: Mac OS X Server Admin — Apple's Abandoned Administration Port

What Port 660 Is

Port 660 is officially assigned by IANA to mac-srvr-admin (MacOS Server Admin), a service that enabled remote management of Mac OS X Server.¹² It sits in the well-known port range (0-1023), reserved for fundamental Internet services.

Both TCP and UDP protocols can use port 660, though TCP was the primary transport for administration commands.

The Service That Was

Mac OS X Server was Apple's server operating system, and port 660 was the channel for Server Admin—the tool that let administrators configure, monitor, and troubleshoot Mac servers remotely. You could manage user accounts, file sharing, mail services, and everything else a server does, all through this single port.

The port was part of Apple's broader server infrastructure, which included AppleShare IP and later Mac OS X Server editions. Administrators needed port 660 open to manage servers that weren't physically accessible.³

Why This Port Is Empty Now

Apple discontinued Mac OS X Server in 2018. The product still exists in a diminished form—macOS Server—but the comprehensive server administration tools that used port 660 are gone. Apple moved core services like file sharing and caching into the standard macOS operating system.

Port 660 remains officially assigned in IANA's registry, but there's nothing listening on it anymore. Not on modern Macs, not on servers, nowhere. It's a reserved address for a service that no longer exists.

The Well-Known Range

Port 660 occupies space in the well-known port range (0-1023), which IANA tightly controls. These ports are reserved for services considered fundamental to Internet operations—HTTP on 80, HTTPS on 443, SSH on 22.

That port 660 sits in this range tells you something about Apple's server ambitions in the early 2000s. They wanted Mac OS X Server administration to be as standard and recognized as any other core Internet service. It didn't work out that way.

Security Considerations

If you see traffic on port 660 today, it's worth investigating. The legitimate service is dead, which means anything using this port is either:

• Legacy Mac OS X Server instances that haven't been updated (a security risk in itself)
• Malware or trojans exploiting the abandoned port number¹
• Custom applications repurposing the port

Check what's listening:

# On macOS/Linux
sudo lsof -i :660

# On Windows
netstat -ano | findstr :660

If something's there and you don't recognize it, investigate further.

What Unassigned Means (And Why 660 Isn't)

Port 660 is not unassigned—it's officially registered to mac-srvr-admin in IANA's database.² But it's functionally abandoned. The difference matters.

Truly unassigned ports in the well-known range are rare and valuable. Unassigned ports in the registered range (1024-49151) are common. Ports in the dynamic/private range (49152-65535) are never assigned—they're meant for temporary use.

Port 660 represents something else: a port that was assigned, used for a specific purpose, and then left behind when that purpose disappeared. It's digital archaeology.

Related Ports

Other Apple server-related ports included:

• 427 - Service Location Protocol, used by macOS for service discovery
• 548 - Apple Filing Protocol (AFP), for file sharing
• 625 - AppleShare IP WebAdmin

Many of these share port 660's fate—officially assigned but rarely used in modern networks.