The JMX module exposes node information through JMX. JMX can be used by either jconsole or VisualVM.
Exposed JMX data include both node level information, as well as instantiated index and shard on specific node. This is a work in progress with each version exposing more information.
The domain under which the JMX will register under can be set using jmx.domain setting. It defaults to {elasticsearch}.
An RMI connector can be started to accept JMX requests. This can be enabled by setting jmx.create_connector to true. An RMI connector does come with its own overhead, make sure you really need it.
When an RMI connector is created, the jmx.port setting provides a port range setting for the ports the rmi connector can open on. By default, it is set to 9400-9500.