You should see the listener port open on each server. You can use the replicated cache debug tool to see what is going on. For information, see Debugging and Monitoring Replicated Caches.

If you see nothing happening while cache operations should be going through, enable trace (LOG4J) or finest (JDK) level logging on net.sf.ehcache.distribution in the logging configuration being used by the debugger. A large volume of log messages will appear. The normal problem is that the CacheManager has not joined the replicated cache topology. Look for the list of cache peers. Finally, the debugger in Ehcache 1.5 has been improved to provide far more information on the caches that are replicated and events which are occurring.