org.jboss.ejb3.remoting.BaseRemoteProxy class has added serialVersionUID attribute which breaks compatibility with EAP 4.2 CP3 clients.

serialver -classpath cp3.jar org.jboss.ejb3.remoting.BaseRemoteProxy
org.jboss.ejb3.remoting.BaseRemoteProxy: static final long serialVersionUID = -2711693270411201590L;

serialver -classpath cp4.jar org.jboss.ejb3.remoting.BaseRemoteProxy
org.jboss.ejb3.remoting.BaseRemoteProxy: static final long serialVersionUID = 1126421850898582900L;

Connecting to CP4 server using CP3 client libraries results in:

Caused by: javax.naming.NamingException: Could not dereference object [Root exception is java.lang.reflect.UndeclaredThrowableException]
at org.jnp.interfaces.NamingContext.getObjectInstanceWrapFailure(NamingContext.java:1152)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:707)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:589)
at javax.naming.InitialContext.lookup(InitialContext.java:392)
at org.jboss.smartfrog.ejb3.SFSBProcessorFactoryImpl$EJB3RequestProcessor.initSession(SFSBProcessorFactoryImpl.java:88)
... 4 more
Caused by: java.lang.reflect.UndeclaredThrowableException
at $Proxy1.createProxy(Unknown Source)
at org.jboss.ejb3.JndiProxyFactory.getObjectInstance(JndiProxyFactory.java:53)
at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304)
at org.jnp.interfaces.NamingContext.getObjectInstance(NamingContext.java:1127)
at org.jnp.interfaces.NamingContext.getObjectInstanceWrapFailure(NamingContext.java:1144)
... 8 more
Caused by: java.rmi.MarshalException: Failed to communicate. Problem during marshalling/unmarshalling; nested exception is:
java.io.InvalidClassException: org.jboss.ejb3.remoting.BaseRemoteProxy; local class incompatible: stream classdesc serialVersionUID = 1126421850898582900, local class serialVersionUID = -2711693270411201590
at org.jboss.remoting.transport.socket.SocketClientInvoker.handleException(SocketClientInvoker.java:122)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.transport(MicroSocketClientInvoker.java:646)
at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:122)
at org.jboss.remoting.Client.invoke(Client.java:1634)
at org.jboss.remoting.Client.invoke(Client.java:548)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:62)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.aspects.remoting.IsLocalInterceptor.invoke(IsLocalInterceptor.java:48)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.aspects.remoting.PojiProxy.invoke(PojiProxy.java:61)
... 13 more
Caused by: java.io.InvalidClassException: org.jboss.ejb3.remoting.BaseRemoteProxy; local class incompatible: stream classdesc serialVersionUID = 1126421850898582900, local class serialVersionUID = -2711693270411201590
at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:562)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1732)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1945)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1869)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at org.jboss.aop.joinpoint.InvocationResponse.readExternal(InvocationResponse.java:122)
at java.io.ObjectInputStream.readExternalData(ObjectInputStream.java:1792)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1751)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1945)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1869)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at org.jboss.remoting.serialization.impl.java.JavaSerializationManager.receiveObjectVersion2_2(JavaSerializationManager.java:239)
at org.jboss.remoting.serialization.impl.java.JavaSerializationManager.receiveObject(JavaSerializationManager.java:133)
at org.jboss.remoting.marshal.serializable.SerializableUnMarshaller.read(SerializableUnMarshaller.java:120)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.versionedRead(MicroSocketClientInvoker.java:957)
at org.jboss.remoting.transport.socket.MicroSocketClientInvoker.transport(MicroSocketClientInvoker.java:586)
at org.jboss.remoting.MicroRemoteClientInvoker.invoke(MicroRemoteClientInvoker.java:122)
at org.jboss.remoting.Client.invoke(Client.java:1634)
at org.jboss.remoting.Client.invoke(Client.java:548)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:62)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.aspects.remoting.IsLocalInterceptor.invoke(IsLocalInterceptor.java:48)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.aspects.remoting.PojiProxy.invoke(PojiProxy.java:61)
at $Proxy1.createProxy(Unknown Source)
at org.jboss.ejb3.JndiProxyFactory.getObjectInstance(JndiProxyFactory.java:53)
at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304)
at org.jnp.interfaces.NamingContext.getObjectInstance(NamingContext.java:1127)
at org.jnp.interfaces.NamingContext.getObjectInstanceWrapFailure(NamingContext.java:1144)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:707)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:589)
at javax.naming.InitialContext.lookup(InitialContext.java:392)
at org.jboss.smartfrog.ejb3.SFSBProcessorFactoryImpl$EJB3RequestProcessor.initSession(SFSBProcessorFactoryImpl.java:88)
at org.jboss.smartfrog.ejb3.SFSBProcessorFactoryImpl$EJB3RequestProcessor.processRequest(SFSBProcessorFactoryImpl.java:53)
at org.jboss.smartfrog.loaddriver.CompoundRequestProcessorFactoryImpl$CompoundRequestProcessor.processRequest(CompoundRequestProcessorFactoryImpl.java:42)
at org.jboss.smartfrog.loaddriver.LoadDriverImpl$Runner.run(LoadDriverImpl.java:80)
at java.lang.Thread.run(Thread.java:619)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemoteInterceptor.java:74)
... 17 more