How to config Ehcache using RMI - rmi

Question

Is the case, I have two web applications running on two different tomcats, each have two applications on tomcat. Now the requirement is applied on the two shared tomcat ehcache cache.
In one tomcat this is the configuration:
<cacheManagerPeerProviderFactory
class="net.sf.ehcache.distribution.RMICacheManagerPeerProviderFactory"
properties="peerDiscovery=automatic, multicastGroupAddress=239.0.0.88,
multicastGroupPort=4446, timeToLive=32"/>
<cacheManagerPeerListenerFactory
class="net.sf.ehcache.distribution.RMICacheManagerPeerListenerFactory"
properties="socketTimeoutMillis=10000"/>
In addition a tomcat, the configuration is as follows:
<cacheManagerPeerProviderFactory
class="net.sf.ehcache.distribution.RMICacheManagerPeerProviderFactory"
properties="peerDiscovery=automatic, multicastGroupAddress=239.0.0.81,
multicastGroupPort=4440, timeToLive=32"/>
<cacheManagerPeerListenerFactory
class="net.sf.ehcache.distribution.RMICacheManagerPeerListenerFactory"
properties="socketTimeoutMillis=10000"/>
But when tomcat starts, it throws the following exception:
[2011-04-20 10:57:08] [INFO] [system.out] [10:57:08,676 WARN [ehcache.distribution.RMIAsynchronousCacheReplicator] Unable to send message to remote peer. Message was: null
java.util.ConcurrentModificationException
at java.util.ArrayList.writeObject(ArrayList.java:573)
at sun.reflect.GeneratedMethodAccessor195.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1469)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518)
at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:422)
at net.sf.ehcache.Element.writeObject(Element.java:787)
at sun.reflect.GeneratedMethodAccessor150.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1469)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:330)
at net.sf.ehcache.distribution.EventMessage.writeObject(EventMessage.java:134)
at sun.reflect.GeneratedMethodAccessor149.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1469)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:330)
at java.util.ArrayList.writeObject(ArrayList.java:570)
at sun.reflect.GeneratedMethodAccessor195.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1469)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:330)
at sun.rmi.server.UnicastRef.marshalValue(UnicastRef.java:274)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:133)
at net.sf.ehcache.distribution.RMICachePeer_Stub.send(Unknown Source)
at net.sf.ehcache.distribution.RMIAsynchronousCacheReplicator.flushReplicationQueue(RMIAsynchronousCacheReplicator.java:317)
at net.sf.ehcache.distribution.RMIAsynchronousCacheReplicator.replicationThreadMain(RMIAsynchronousCacheReplicator.java:119)
at net.sf.ehcache.distribution.RMIAsynchronousCacheReplicator.access$100(RMIAsynchronousCacheReplicator.java:56)
at net.sf.ehcache.distribution.RMIAsynchronousCacheReplicator$ReplicationThread.run(RMIAsynchronousCacheReplicator.java:376)
]