What Lives Here
Port 1577 tells two different stories depending on who you ask.
Ask IANA, and port 1577 is officially registered for hypercube-lm—a license manager service registered by Christopher McLendon.1 The registration is straightforward: both TCP and UDP, service name hypercube-lm, purpose unstated beyond the name itself.
Ask a network administrator or search the web, and port 1577 is the port for IBM Rational ClearCase—a version control system used at large enterprises for software configuration management.2 ClearCase uses this port for Remote Procedure Calls (RPC) that let clients check in files, check out files, create branches, merge changes, and perform all the operations that keep massive codebases synchronized across hundreds of developers.
Both answers are true. This is what happens in the registered port range (1024-49151): official assignments don't prevent other uses, and widespread adoption sometimes overshadows the original intent.
The Registered Range
Port 1577 sits in the registered port range (1024-49151). These ports are assigned by IANA through formal processes—IETF Review, IESG Approval, or Expert Review3—but unlike the well-known ports below 1024, registered ports don't require special privileges to use.
This creates a practical tension. Someone can register a port for hypercube-lm. Someone else can build ClearCase and decide it needs a port for RPC communication. Both can use 1577. The registry becomes a record of intent, not a guarantee of exclusive use.
ClearCase's Story
IBM Rational ClearCase (now IBM DevOps Code ClearCase) has a long history in enterprise version control. It was developed by Atria Software and first released in 1992 on Unix, later ported to Windows. Atria merged with Pure Software to form PureAtria in 1996, which was acquired by Rational Software in 1997, which was purchased by IBM in 2003.4
For organizations with hundreds or thousands of developers working on the same codebase, ClearCase became infrastructure. And infrastructure needs reliable network communication. Port 1577 became the door through which ClearCase clients talked to ClearCase servers.
When you see port 1577 open on a corporate network, it's probably ClearCase. The version control system's widespread enterprise adoption made this association more common than the original hypercube-lm registration.
What Is hypercube-lm?
The official registration provides almost no details. "hypercube-lm" suggests a license manager (the "-lm" suffix is a common pattern for license management services). But there's little public documentation about what software it served, when it was actively used, or whether it's still deployed anywhere.
This isn't unusual. The IANA registry contains thousands of port assignments for services that had legitimate needs at the time of registration but never achieved widespread adoption. The registry preserves the intent—someone needed this port for something real—even when history has moved on.
Security Considerations
If you're running ClearCase, port 1577 needs to be accessible between clients and servers. This is RPC communication carrying version control operations, which means:
- Firewall rules matter — Block this port externally unless you need remote ClearCase access
- Authentication is handled by ClearCase — The port itself provides no security
- Monitor for unexpected traffic — If you're not running ClearCase (or hypercube-lm), this port should be closed
Checking What's Listening
To see if anything is listening on port 1577 on your system:
Linux/Mac:
Windows:
If you see a process listening and you're not running ClearCase or any license manager software, investigate what's bound to this port.
The Gap Between Registry and Reality
Port 1577 isn't broken or misconfigured. It's functioning exactly as the registered port range is designed to function: as a space where organizations can register their intent to use a port for a specific purpose, while the reality of what actually runs on that port evolves based on which software achieves widespread deployment.
The official record says hypercube-lm. The field experience says ClearCase. Both are part of the story of this port. The registry documents what was planned. The Internet documents what actually happened.
Related Ports
- Port 371 — ClearCase Albd (ClearCase's location broker daemon)
- Port 27000-27009 — FlexLM license manager (another common license management port range)
- Port 1080 — SOCKS proxy (another registered port with multiple real-world uses)
Frequently Asked Questions
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