Although scalability in the number of clients is not a major concern for typical JMX deployments, it is worrying that the number of threads in the server increases linearly with the number of clients, regardless of the transport in use. In particular, the LeaseManager that is used only to handle client lease expiry does not really need to have one permanent thread per client. An unbounded thread pool would be much better. It needs to be unbounded because lease expiry ends up calling user code, namely removeNotificationLIstener on every MBean that had a listener added for that client, plus EventForwarder.close() at the end.