Port 3604: BMC JMX Port — The Registered Port Nobody Talks About

What This Port Is

Port 3604 sits in the registered port range (1024–49151) and carries an official IANA assignment: BMC JMX Port, registered in September 2002.¹

That name tells a specific story. JMX stands for Java Management Extensions, a standard Java technology for remotely monitoring and managing JVM-based applications — things like heap memory, thread counts, and application-specific metrics. BMC Software, a major IT operations management company, registered this port for use with their monitoring products.

In practice, you are unlikely to encounter anything running on port 3604 on a typical system. The registration exists in the registry. Traffic on this port in the wild is rare.

The Registered Port Range

Ports 1024–49151 are registered ports — organizations apply to IANA, get a port number assigned, and agree to document their use. Unlike the well-known ports (0–1023), no elevated privileges are required to bind a registered port. Unlike the ephemeral range (49152–65535), these are not intended for temporary outbound connections.

The range contains thousands of entries like this one: officially claimed, rarely discussed, occasionally never meaningfully deployed. Registration is a statement of intent, not a guarantee of adoption.

JMX and What It Does

JMX remote connections work over RMI (Remote Method Invocation) and typically require opening two ports: one for the registry and one for the actual data connection. BMC's PATROL monitoring platform and related products use JMX to observe Java application servers — Tomcat, WebSphere, JBoss, and similar.²

If you run BMC PATROL agents monitoring Java applications, port 3604 may be relevant. If you don't, it almost certainly isn't.

How to Check What's Listening Here

If you see activity on port 3604 and want to know what's responsible:

Linux / macOS:

# Show the process listening on port 3604
ss -tlnp | grep 3604
# or
lsof -i :3604

Windows:

netstat -ano | findstr :3604

Take the PID from the output and look it up:

# Linux/macOS
ps aux | grep <PID>

# Windows (in Task Manager or)
tasklist | findstr <PID>

Should You Be Concerned?

An unexpected process on port 3604 deserves the same scrutiny as any unexpected listener — identify it, verify it, block it if you can't explain it. There are no documented exploit campaigns targeting this port specifically, but an unknown listener is always worth investigating regardless of port number.

If you're running BMC monitoring software and this port is active, that's expected. If you're not, it shouldn't be there.