An event acknowledgement allows the receiver to explicitly respond to the sender after processing an event.

Consider a chat message submission.

Without acknowledgements, the client sends a message and does not know whether the server successfully processed it.

With acknowledgements:

1. The client emits an event.
2. The server receives the event.
3. The server validates the payload.
4. The server processes the event.
5. The server calls the acknowledgement callback.
6. The client receives the result.

This is useful for:

• Confirming message delivery to the server.
• Saving records to a database.
• Validating user actions.
• Confirming room membership.
• Handling failed operations.

An acknowledgement confirms that the receiving handler responded. It does not automatically guarantee that a message was delivered to every intended user or persisted permanently.