I am trying to configure Weblogic 10.3.5 with Coherence cluster and two nodes. Everything is running on my local machine. I configured Coherence with WLST and now trying to run both nodes. One node starts and second fails with following exception: 2012-05-10 12:57:37.681/6.175 Oracle Coherence GE 3.6.0.4 (thread=Environment.Background.Executor:Thread-1, member=n/a): Error while starting cluster: java.lang.NullPointerException at com.tangosol.coherence.component.net.TcpRing.ensureSelector(TcpRing.CDB:7) at com.tangosol.coherence.component.net.TcpRing.setServerSocketChannel(TcpRing.CDB:20) at com.tangosol.coherence.component.net.Cluster.onStart(Cluster.CDB:510) at com.tangosol.coherence.component.net.Cluster.start(Cluster.CDB:11) at com.tangosol.coherence.component.util.SafeCluster.startCluster(SafeCluster.CDB:3) at com.tangosol.coherence.component.util.SafeCluster.restartCluster(SafeCluster.CDB:7) at com.tangosol.coherence.component.util.SafeCluster.ensureRunningCluster(SafeCluster.CDB:26) at com.tangosol.coherence.component.util.SafeCluster.start(SafeCluster.CDB:2) at com.tangosol.net.CacheFactory.ensureCluster(CacheFactory.java:998) at com.tangosol.net.DefaultConfigurableCacheFactory.ensureServiceInternal(DefaultConfigurableCacheFactory.java:923) at com.tangosol.net.DefaultConfigurableCacheFactory.ensureService(DefaultConfigurableCacheFactory.java:892) at com.oracle.coherence.environment.extensible.ExtensibleEnvironment.ensureService(ExtensibleEnvironment.java:497) at com.tangosol.net.DefaultConfigurableCacheFactory.ensureCache(DefaultConfigurableCacheFactory.java:874) at com.tangosol.net.DefaultConfigurableCacheFactory.configureCache(DefaultConfigurableCacheFactory.java:1231) at com.tangosol.net.DefaultConfigurableCacheFactory.ensureCache(DefaultConfigurableCacheFactory.java:290) at com.oracle.coherence.common.util.ObjectProxyFactory.ensureCache(ObjectProxyFactory.java:285) at com.oracle.coherence.common.util.ObjectProxyFactory.onDependenciesSatisfied(ObjectProxyFactory.java:307) at com.oracle.coherence.environment.extensible.dependencies.DependencyTracker.processLater(DependencyTracker.java:204) at com.oracle.coherence.environment.extensible.dependencies.DependencyTracker.processLater(DependencyTracker.java:46) at com.oracle.coherence.common.events.processing.AbstractAsynchronousEventProcessor$1.run(AbstractAsynchronousEventProcessor.java:53) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) I configured servers to run on the same port and enabled Unicast Port Auto Adjust, thinking that Coherence would be smart enough to figure out that port is in use. But it is not that smart! But Oracle Metalink has more information about it:

Cause Coherence 3.6 has since Patch 2 been enhancing its network throughput by using two open UDP ports for each member. For this Coherence picks Unicast listener + 1 for the second port. It has been implemented as a part of COH-3722. Note that Coherence 3.6.1 and onwards will not have the NullPointerException but a more meaningful error message. Solution Separate nodes which run on the same machine by at least two ports. For example: When you specify localport=6000 for one node, it will also use port 6001. The next node you can specify to use localport=6002 will also use 6003 Again the next node you can specify to use localport=6004 will also use 6005 etc
I reconfigured Unicast ports accordingly and the problem is solved!