This is most likely a configuration problem on the Linux machine or the management properties specified to run the application.
You should check the following:
Check if the hostname correctly resolves to the host address.
Run "hostname -i" command. If it reports 127.0.0.1, JConsole would not be able to connect to the JVM running on that Linux machine. To fix this issue, edit /etc/hosts so that the hostname resolves to the host address.
Check if the Linux machine is configured to accept packets from the host where JConsole runs on to connect to the application.
Packet filtering is built in the Linux kernel. You can run "/sbin/iptables --list" to determine if an external client is allowed to connect to the JMX agent created for remote management. You can use the following command to add a rule to allow an external client such as JConsole to connect:
/usr/sbin/iptables -I INPUT -s jconsole-host -p tcp --destination-port jmxremote-port -j ACCEPT
where jconsole-host is either the hostname or the host address on which JConsole runs on and jmxremote-port is the port number set for com.sun.management.jmxremote.port for remote management.
See http://java.sun.com/j2se/1.5.0/docs/guide/management/faq.html for more details