How does jconsole know of all monitored JVMs in system?

When you run jconsole, the tab named "local" lists JVMs running and their PIDs. By what mechanism is it able to 'know' which JVMs are running that have been started with the arguments that enable JMX management?
Does jconsole connect to JVMs or to MBeanServers? (Assume each JVM has multiple MBeanServers, and each MBeanServer has multiple domains.)
Also, what's the difference between using the 'remote' and 'advanced' tabs to connect to a JVM? They both have usernames and passwords, but while the 'remote' tab has a host and port, the 'advanced' tab has a URL that contains a host and port within it. So what's the difference - when would you pick one method of connection over another?
Thanks.

If jconsole connects to MBeanServers rather than
JVMs, then how can it tell the difference between
multiple MBeanServers that have been started by a
single JVM?JConsole connects to a given JMX connector server which is associated with a given MBeanServer at creation time.
For example, if I have a simple application (i.e. one
JVM) that starts up two MBeanServers in its main
method, using
MBeanServerFactory.createMBeanServer(name). To start
the application, you run the JVM with the
com.sun.management.jmxremote and
com.sun.management.jmxremote.port variables.
How will jconsole know to differentiate between the
two MBeanServers? After all, there's only one JVM -
and it's been started with only one port number.In your example JConsole will not see any of your MBeanServers. It'll see the platform MBeanServer which is the one used by the out-of-the-box management agent.
The next question I have is regarding the JVM - does
any JVM that's started locally show up in the "local"
tab of JConsole (because the JVM is always
instrumented by default - true?), or does it only
appear if you run it with the
com.sun.management.jmxremote variable?The new Attach API in JDK 6 allows JConsole 6 to show all the JVMs running on the local machine although you will only be able to connect to the ones running on JDK 6 (and JDK 5.0 if started with the com.sun.management.jmxremote or com.sun.management.jmxremote.port system properties).
JConsole 5 only shows the JVMs running on JDK 5.0 and started with the com.sun.management.jmxremote or com.sun.management.jmxremote.port system properties.
Have a look at the link below for more detailed info:
http://java.sun.com/javase/6/docs/technotes/guides/management/index.html
Regards,
Luis-Miguel Alventosa
Java SE JMX/JConsole development team
Sun Microsystems, Inc.
http://blogs.sun.com/lmalventosa/

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