1. Concepts

1.1 Definitions

The notion of communication by message between applications – or between programs – has always existed in computing. In practice, we can say that programs communicate with each other by exchanging messages: these are either the arguments they exchange when they call each other with a CALL –, which can be a set of arguments or a data structure –, or the data they exchange over a network via communication functions.

In object-oriented programming, the vocabulary used today refers to objects communicating with each other via messages.

Finally, interpersonal communication, or messaging, involves the exchange of messages between individuals.

What we're interested in here is the ability to exchange messages...