NATS messaging involves the electronic exchange of data among computer applications.
NATS provides a layer between the application and the underlying physical network. Application data is encoded as a message and sent by the publisher. The message is received, decoded, and processed by one or more subscribers. A subscriber can process a NATS message asynchronously or synchronously.
NATS makes it easy for programs to communicate across different environments, languages, and systems because all a client has to do is parse the message. NATS lets programs share common message-handling code, isolate resources and interdependencies, and scale by easily handling an increase in message volume.
Asynchronous processing uses a callback message handler to process messages. When a message arrives, the registered callback handler receives control to process the message. The client or consuming application is not blocked from performing other work while it is waiting for a message. Asynchronous processing lets you create multi-threaded dispatching designs.
Synchronous processing requires that application code explicitly call a method to process an incoming message. Typically an explicit call is a blocking call that suspends processing until a message becomes available. If no message is available, the period for which the message processing call blocks is set by the client. Synchronous processing is typically used by a server whose purpose is to wait for and process incoming request messages, and to send replies to the requesting application.