ClientSessions Guarantees
ClientSession instances can be registered with an optional SendAcknowledgementHandler. This allows your client code to be notified asynchronously when sent messages have successfully reached the server. This unique HornetQ feature, allows you to have full guarantees that sent messages have reached the server without having to block on each message sent until a response is received. Blocking on each messages sent is costly since it requires a network round trip for each message sent. By not blocking and receiving send acknowledgements asynchronously you can create true end to end asynchronous systems which is not possible using the standard JMS API. For more information on this advanced feature please see the section Chapter 20, Guarantees of sends and commits.