Hi, After some further experimentation I think I finally found the critical part. I can reproduce the misbehaviour by adding a trivial ExceptionListener to the connection of the topic example included with the Messaging distribution (org.jboss.example.jms.topic.TopicExample): | ... | connection = cf.createConnection(); | connection.setExceptionListener(new ExceptionListener() { | public void onException(JMSException jmse) { | } | }); | ... | You also have to take care that the subscriber is running for some time (e.g. suppress publishing the message it is waiting for and extending the waiting time to, say, a minute). During this time you can look at DEBUG output and/or repeatedly run netstat to see that a new connection to the messaging port is opened and closed every two seconds: | ... | [java] 11:59:37,410 DEBUG @main [MessageIdGeneratorFactory] checked out MessageIdGenerator for server.0, reference count is 1 | [java] 11:59:38,160 DEBUG @main [JBossSession] attempting to create consumer for destination:JBossTopic[testTopic] | [java] 11:59:39,457 DEBUG @Timer-0 [MicroSocketClientInvoker] Setting ClientSocket class name to: org.jboss.jms.client.remoting.ClientSocketWrapper | [java] 11:59:39,457 DEBUG @Timer-0 [SocketClientInvoker] Setting SocketClientInvoker::timeout to: 1000 | [java] 11:59:39,457 DEBUG @Timer-0 [MicroSocketClientInvoker] Setting ClientSocket class name to: org.jboss.jms.client.remoting.ClientSocketWrapper | [java] 11:59:39,457 DEBUG @Timer-0 [SocketClientInvoker] Setting SocketClientInvoker::timeout to: 1000 | [java] 11:59:39,472 DEBUG @Timer-0 [MicroRemoteClientInvoker] connect called for: org.jboss.remoting.transport.socket.SocketClientInvoker@15356d5 | [java] 11:59:39,472 DEBUG @Timer-0 [MicroRemoteClientInvoker] disconnect called for: org.jboss.remoting.transport.socket.SocketClientInvoker@15356d5 | [java] 11:59:41,472 DEBUG @Timer-0 [MicroSocketClientInvoker] Setting ClientSocket class name to: org.jboss.jms.client.remoting.ClientSocketWrapper | [java] 11:59:41,472 DEBUG @Timer-0 [SocketClientInvoker] Setting SocketClientInvoker::timeout to: 1000 | [java] 11:59:41,472 DEBUG @Timer-0 [MicroSocketClientInvoker] Setting ClientSocket class name to: org.jboss.jms.client.remoting.ClientSocketWrapper | [java] 11:59:41,472 DEBUG @Timer-0 [SocketClientInvoker] Setting SocketClientInvoker::timeout to: 1000 | [java] 11:59:41,472 DEBUG @Timer-0 [MicroRemoteClientInvoker] connect called for: org.jboss.remoting.transport.socket.SocketClientInvoker@fb6354 | [java] 11:59:41,488 DEBUG @Timer-0 [MicroRemoteClientInvoker] disconnect called for: org.jboss.remoting.transport.socket.SocketClientInvoker@fb6354 | ... | This is not the initial problem of this thread (JMS Exceptions / Mismatch of JBossSerialization version), but I'm rather certain that it is related to this issue, as it leads to connection timeouts. Anyway, the frequent connection creation is a problem on it's own right. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4002240#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...