When we use a client acknowledgement mode in JMS (I am using Websphere MQ and WAS), the MDB sends the acknowledgement to whom (the docs say to the JMS server).
But in this case, the JMS server means what: the WebSphere MQ which actually has all the queues and the messages or the web sphere application server that is connecting to the websphere MQ.
Acknowledgements, no matter the type, are always sent to the JMS server. Message producers and consumers never communicate directly due to the asynchronous nature of JMS.
Are you using connection factories to obtain a connection? If so, look at the broker url configuration in those factories. You should find the connection url points to WSMQ brokers. So, when you get a connection from a connection factory, the client connection goes directly to the JMS server in WSMQ.
