Java Message Service (JMS) Question:

Point-To-Point (PTP). This model allows exchanging messages via queues created for some purposes. A client can send and receive messages from one or several queues. PTP model is easier than pub/sub model.
A durable subscription gives a subscriber the freedom of receiving all messages from a topic, whereas a non-durable subscription doesn't make any guarantees about messages sent by others when a client was disconnected from a topic.