消息队列实现双向通信

消息队列实现双向通信应该用两个消息来实现，单个消息队列是单向的，两个单向的消息队列，实现双向。

Where can I find a bidirectional messaging queue?

If you need an immediate reply to a message, then you shouldn't use a message queue. 
If you want a reply at some point in the future, then all message queue systems can be bidirectional, you just use different queues. For instance:
System A put a message on Queue X.
System B receives messages on Queue X.
System B processes messages from Queue X and puts replies on Queue Y. 
System A receives messages on Queue Y.