JBoss.org Community Documentation

22.7.11. JGroups Troubleshooting

Nodes do not form a cluster

Make sure your machine is set up correctly for IP multicast. There are 2 test programs that can be used to detect this: McastReceiverTest and McastSenderTest. Go to the $JBOSS_HOME/server/all/lib directory and start McastReceiverTest, for example:

java -cp jgroups.jar org.jgroups.tests.McastReceiverTest -mcast_addr -port 5555 

Then in another window start McastSenderTest:

java -cp jgroups.jar org.jgroups.tests.McastSenderTest -mcast_addr -port 5555

If you want to bind to a specific network interface card (NIC), use -bind_addr, where is the IP address of the NIC to which you want to bind. Use this parameter in both the sender and the receiver.

You should be able to type in the McastSenderTest window and see the output in the McastReceiverTest window. If not, try to use -ttl 32 in the sender. If this still fails, consult a system administrator to help you setup IP multicast correctly, and ask the admin to make sure that multicast will work on the interface you have chosen or, if the machines have multiple interfaces, ask to be told the correct interface. Once you know multicast is working properly on each machine in your cluster, you can repeat the above test to test the network, putting the sender on one machine and the receiver on another.