What Runs Here
Port 612 is officially assigned to HMMP Indication (hmmp-ind), a protocol designed for web-based enterprise management in the 1990s.1 HMMP stands for Hypermedia Management Protocol, part of an industry effort to create cross-platform management systems that could be accessed through web browsers.
The protocol was proposed by Computer Associates and Microsoft as part of the Web-Based Enterprise Management (WBEM) initiative.2 The idea was ambitious: use HTTP-like protocols to manage servers, applications, and network devices across different platforms and vendors.
It didn't become the standard. Most of that vision migrated to other technologies—WMI on Windows, SNMP for network devices, and eventually REST APIs for modern infrastructure management.
What Well-Known Means
Port 612 sits in the well-known ports range (0-1023), which is reserved for services assigned by the Internet Assigned Numbers Authority (IANA).3 Getting a port in this range requires official registration and approval.
That registration happened decades ago. The port was allocated when HMMP seemed like it might matter. It still holds the assignment today, even though the protocol has faded into obscurity.
This is normal. The well-known range contains many ports assigned to services that never became widely adopted. Port allocations are rarely revoked—they're kept to avoid conflicts if old systems are still running somewhere.
The Unofficial Story
While HMMP Indication is the official assignment, port 612 has occasionally been observed in use by Mac OS X RPC-based services, particularly NetInfo in older versions of Mac OS X Server.4
NetInfo was Apple's network directory service before they switched to LDAP and Open Directory. It used a range of ports (600-1023) for RPC communication, and port 612 sometimes appeared in those configurations.
This is a common pattern: when official port assignments aren't actively used, other services sometimes occupy the space—especially in private networks where IANA assignments don't strictly apply.
How to Check What's Listening
If you want to see whether anything is actually using port 612 on your system:
On Linux or macOS:
On Windows:
Using nmap to scan a remote host:
Most systems won't show anything. Port 612 is usually silent.
Why Unassigned Use Matters
Ports like 612 illustrate something important about how the Internet's port system works: official assignments don't guarantee actual usage.
The well-known range was designed when people believed we could assign every important service a permanent, globally recognized port number. That worked for foundational protocols—HTTP on 80, HTTPS on 443, SSH on 22, DNS on 53.
But enterprise management protocols? Those come and go. Technologies change. Standards compete and one wins while others fade. The port assignments remain as historical artifacts.
This doesn't make port 612 useless. It means the port is available in the official registry but not occupied in practice. If you're running a private network and need a port for internal services, technically you shouldn't use 612 because it's assigned. Practically? Most networks have services running on officially assigned ports without conflict because those official services aren't actually running.
The port system assumes we'll follow the assignments. The reality is more chaotic and more functional than the plan suggested.
Related Ports
- Port 613 — HMMP Operation (hmmp-op), the companion to HMMP Indication1
- Port 411 — Direct Connect Hub, another example of an assigned-but-obscure protocol
- Port 800-899 — Various enterprise management protocols from the same era, many now defunct
Frequently Asked Questions
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