What is an application?
An application is any computer program or a group of them.
An application could also be a micro-service, IoT device (sensor), mainframe process, etc. Users may even write applications in different programming languages if they support one of the selected protocols.
Why do we need applications?
In Event-Driven Architecture (EDA), an application must be a
consumer, or both. Applications must also use the protocols the server supports if they wish to connect and exchange messages.
Applications: producers and consumers
The above diagram describes a message communication traveling through a channel between a PRODUCER application and a CONSUMER application.