Port 613: HMMP Operation — The NetInfo port that Apple left behind

Port 613 sits in the well-known ports range (0-1023), officially assigned by IANA to "hmmp-op"—HMMP Operation. But if you encountered this port in the wild during the 2000s, you weren't seeing mobility management. You were seeing NetInfo, Apple's directory service that lived in Mac OS X from 10.0 through 10.4.

This is a port where official assignment and actual use diverged completely.

What HMMP Operation Was Supposed to Be

HMMP (Host Mobility Management Protocol) was designed in the early 2000s as a mobility management solution for 3G-IP networks.¹ The protocol extended SIP (Session Initiation Protocol) to handle roaming and handoffs as mobile devices moved between networks—what engineers call "macro mobility."

The protocol had ambitions: support real-time multimedia applications on mobile terminals, spoof constant endpoints for TCP connections, enable seamless domain and subnet handoffs. Port 613 was assigned as the operational port for this protocol.

But HMMP never gained widespread adoption. The port number was registered, the draft specifications were written, and then the protocol faded into obscurity as other mobility solutions won out.

What Port 613 Actually Carried

While HMMP Operation held the official assignment, port 613 became known for something entirely different: NetInfo.²

NetInfo was Apple's network configuration database, inherited from NeXTSTEP when Mac OS X was built on NeXT foundations. It stored critical system information—user accounts, groups, network settings—in a binary database that could be distributed across networks.

Mac OS X used NetInfo as its primary directory service from version 10.0 (2001) through 10.4 Tiger (2005). Port 613 was where NetInfo's RPC-based services communicated.³

For Mac administrators during those years, port 613 wasn't about mobility protocols. It was about managing user directories and system configuration across networked Macs.

The End of NetInfo

Apple began phasing NetInfo out with Mac OS X 10.2, reducing it from network directory management to just local user management.⁴ With Mac OS X 10.5 Leopard in 2007, NetInfo was completely removed and replaced by Open Directory and standard property list files in /var/db/dslocal/.⁵

Port 613 became obsolete overnight for Mac users.

Why This Port Matters

Port 613 demonstrates something unusual in the port number system: the gap between official assignment and actual use.

IANA assigned 613 to HMMP Operation. That's what the registry says. But in practice, the port became associated with an entirely different service—NetInfo—that was never officially registered for that number. When NetInfo disappeared, the port didn't transfer back to HMMP. It simply became quiet.

Today, if you see port 613 in use, it's worth investigating. It's not carrying the official protocol. It's probably not carrying the historical Mac service. It's carrying something else entirely—and that's when unassigned or abandoned ports become interesting from a security perspective.

Checking Port 613

To see what's listening on port 613 on your system:

On Linux or macOS:

sudo lsof -i :613
# or
sudo netstat -tulpn | grep :613

On Windows:

netstat -ano | findstr :613

If something is listening, the command will show you the process ID and name. Most modern systems will show nothing—this port belongs to the past.