Hi thanks for your reply, ive downloaded the jgroups bin and extracted it. I've added the location of the jar files (javagroups-all.jar, jms.jar etc) to the classpath. when I execute this command: java McastReceiverTest.class -mcast_addr 228.1.2.3 -port 45566 it's telling me: Exception in thread "main" java.lang.NoClassDefFoundError: McastReceiverTest/class my dir is /home/jboss/JavaGroups-2.1.1.bin and this is the classpath setting: PATH=/usr/kerberos/bin:/usr/java/j2sdk1.4.2_13//bin:/usr/local/bin:/bin:/usr/bin:/home/jboss/bin:/home/jboss/JavaGroups-2.1.1.bin CLASSPATH=/usr/java/j2sdk1.4.2_13/:/home/jboss/JavaGroups-2.1.1.bin any idea? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4027430#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...