Message queue is a circular queue which transfer data by giving a tag,tag is generally the id of the data package to be transfered and it differentiates the data from one another.
Message queuing allows distributed applications to communicate asynchronously by sending messages between the applications. The messages from the sending application are stored in a queue and are retrieved by the receiving application. The applications send or receive messages through a queue by sending a request to the message queuing system. Sending and receiving applications can use the same message queuing system or different ones, allowing the message queuing system to handle the forwarding of the messages from the sender queue to the recipient queue.
Queued messages can be stored at intermediate nodes until the system is ready to forward them to the next node. At the destination node, the messages are stored in a queue until the receiving application retrieves them from the queue. Message delivery is guaranteed even if the network or application fails. This provides for a reliable communication channel between the applications.
The complexity and details of the underlying model (to store and forward messages between different environments) are handled by the message queuing system. By maintaining this level of abstraction, distributed applications can be developed without the need to worry about the details of how the information is transported.
Because the sending and receiving applications operate independently of one another, the sending application is less dependent on the availability of the remote application, less dependent on the network between them, and less dependent on the computer system on which the receiving application runs. This leads to a higher level of availability for the participating applications.
Messages and message queue operations can be configured by the applications to operate in specific modes. For example, a sending application can specify that queued messages should survive system crashes. As another example, the receiving application can specify a maximum waiting period for a receiving operation from a queue (in case no messages are available yet on the receiving queue).
