What differentiates a synchronous message from an asynchronous message?

A synchronous message is characterized by the requirement for the sender to wait for a reply from the receiver before proceeding. This means that the interaction is closely tied to the flow of control between the communicating parties. In scenarios involving synchronous messaging, the sender remains blocked until a response is received, ensuring that both parties are effectively in sync with the communication process.

This reinforces the idea that synchronous messaging often involves real-time exchanges, such as in phone calls or video conferencing, where immediate feedback is essential for the interaction to progress smoothly. This aspect of requiring a response and maintaining a direct line of communication is what distinctly sets synchronous messages apart from asynchronous ones, where the sender can continue with other tasks without waiting for an immediate response. Understanding this fundamental difference is key in modeling communication systems effectively.