Port 371: ClearCase albd — The Broker That Routes Your Code

Port 371 is where ClearCase talks to the world. More specifically, it's where the Atria Location Broker Daemon (albd) listens—the broker that coordinates every ClearCase operation across a network.¹²

What It Does

When a ClearCase client needs to access a versioned file, check out code, or query a repository, it doesn't connect directly to the right service. It connects to port 371 first.³

The albd daemon answers. It figures out what you need—a VOB server, a view server, a lock manager—and tells you which port that service is running on. Then you connect directly to that service. The broker steps aside.⁴

Port 371 is the dispatcher. Every ClearCase operation starts here.

How It Works

ClearCase is an enterprise version control system built for large teams—hundreds or thousands of developers working on the same codebase.⁵ It uses a distributed client-server architecture where different services run on different ports.

The Atria Location Broker Daemon is the coordinator:

1. Client sends a Remote Procedure Call (RPC) to port 371: "I need access to this VOB"
2. albd checks if the requested service is running—if not, it starts it
3. albd responds with the service's port number
4. Client connects directly to that service on the assigned port
5. albd is no longer involved in that conversation

It's a handshake protocol. The broker introduces you, then gets out of the way.³

The History: Atria Software

Port 371 has "Atria" in its name because Atria Software is the company that built ClearCase.⁶

David Leblang, Paul Levine, David Jabs, and others founded Atria on January 11, 1990. Some had worked on an earlier system called DSEE (Domain Software Engineering Environment) at Apollo Computer. When Hewlett-Packard bought Apollo in 1989, they left to build something better.⁶

ClearCase 1.0 shipped in 1992.⁶ The Atria Location Broker Daemon was there from the beginning, coordinating all network communication.⁷

Rational Software bought Atria in 1996. IBM bought Rational in 2003. HCL bought IBM's software portfolio in 2019. The product is now called IBM DevOps Code ClearCase or HCL VersionVault.⁵⁶

But the daemon is still called albd_server. The port is still 371. The name "Atria" remains in every services file, a fossil record of the startup that started it all.

Port 371 in Practice

The IANA officially assigned port 371 to ClearCase albd for both TCP and UDP.¹ Every ClearCase host must have this entry in /etc/services:

albd    371/udp    # Atria Location Broker Daemon
albd    371/tcp    # Atria Location Broker Daemon

All ClearCase hosts in a network must use the same port for albd. If you change it on one machine, you must change it everywhere.²

For ClearCase to work through firewalls, port 371 (both TCP and UDP) must be open to all ClearCase servers.²

Security Considerations

Port 371 is a well-known port, officially registered with IANA. ClearCase installations require it.

However, like any network service, it can be exploited:

• Trojan/malware has used port 371 in the past for communication⁸
• Port conflicts occur when another service tries to bind to 371, causing the "address already in use" error⁹
• Authentication is critical—the albd service runs with specific account permissions that control access to versioned repositories

If you see unexpected traffic on port 371 and you're not running ClearCase, investigate immediately. Check what's listening:

# Linux/macOS
sudo lsof -i :371
sudo netstat -tulpn | grep 371

# Windows
netstat -ano | findstr :371

Why This Port Matters

Port 371 is a coordination port—it doesn't carry your actual data, but it routes every request to the service that does.

Without port 371, ClearCase doesn't work. The broker is the entry point. It's how clients find servers, how services register themselves, how the distributed system stays synchronized.

The daemon name preserves the history: Atria built the system. The companies changed. The acquisitions happened. But the code still runs. The port still listens. The broker still routes requests for teams building software that millions of people depend on.

Related Ports

• Port 22 (SSH): Modern alternative for Git version control with secure transport
• Port 3690 (SVN): Subversion version control, another centralized system
• Dynamic ports (1024-65535): Where the actual ClearCase services (VOB servers, view servers) run after albd assigns them