Port 424: opc-job-track — The Mainframe's Job Tracker

Port 424 carries job tracking communications for IBM Operations Planning and Control (OPC), now known as IBM Workload Scheduler for z/OS. This port monitors and tracks batch jobs running across mainframe and distributed systems in enterprise computing environments.

What This Port Does

Port 424 handles the "opc-job-track" service—the tracking component of IBM's workload automation system.¹ While its sibling port 423 starts jobs, port 424 keeps track of them as they run.

In large enterprises, thousands of batch jobs execute every day—payroll processing, database backups, report generation, data transformations. These jobs depend on each other in complex chains. Port 424 carries the status updates that tell the scheduler which jobs are running, which have finished, which are stuck, and which are ready to start.

The protocol works over both TCP and UDP on port 424, though TCP is more common for the guaranteed delivery of job status information.²

The Operations Planning Problem

IBM created Operations Planning and Control in the mainframe era to solve a fundamental problem: coordinating work across computing infrastructure at enterprise scale.

Before automated workload scheduling, operators manually submitted jobs and tracked their progress on paper. Miss a dependency and a critical job fails. Start something too early and you waste expensive computing time. Start it too late and business processes stop.

OPC automated this coordination. Port 423 handles "opc-job-start"—the command to begin execution. Port 424 handles "opc-job-track"—the continuous monitoring of job status. Together they form the control loop that keeps enterprise batch processing running.

The system evolved from OPC to Tivoli Workload Scheduler for z/OS, then IBM Workload Scheduler for z/OS, but the fundamental architecture remains: a z/OS Controller coordinates Tracker-Agents running on every machine under its control.³

Why Tracking Matters

Starting a job is simple. Knowing it's still running, hasn't hung, is consuming expected resources, will finish on time—that's the hard part.

Port 424 exists because job tracking is distinct from job starting. The start command is a moment. The tracking is continuous. A job might run for minutes or hours. Dependencies might wait for its completion. Other systems might need to know its status.

The tracker monitors execution and reports back through port 424. The controller uses this information to make decisions: release dependent jobs, alert operators to problems, update schedules based on actual completion times.

This separation—start on 423, track on 424—reflects a deep understanding of how batch processing actually works.

Modern Context

IBM Workload Scheduler for z/OS still runs on mainframes across industries: banking, insurance, healthcare, government. These systems process transactions worth billions of dollars daily. The batch jobs they coordinate handle payroll for millions of employees, reconcile accounts, generate regulatory reports.

Port 424 is less visible than ports that carry user traffic, but it's no less critical. When the tracker stops reporting, the scheduler goes blind. Jobs might complete but dependent work never starts. Or worse, jobs fail silently and nobody knows until business processes break hours later.

Security Considerations

Since port 424 carries job control information for critical enterprise systems, it should never be exposed to the public Internet. Access should be restricted to authorized workload scheduler components within the enterprise network.

Unauthorized access to job tracking communications could reveal sensitive information about business processes, timing, and system architecture. Firewall rules should limit port 424 to communication between known scheduler components.

Related Ports

• Port 423 - opc-job-start: IBM Operations Planning and Control job starting (the companion to port 424's tracking)

Checking Port 424

To see if something is listening on port 424:

# On Linux/macOS
sudo lsof -i :424
sudo netstat -tulpn | grep :424

# On Windows
netstat -ano | findstr :424

If you're not running IBM Workload Scheduler and see activity on port 424, investigate—this port should only be used by legitimate workload automation software.