Events
Due to the client-server relationship of JAUS Components, communication in JAUS follows a Request-Response (or Query-Report) model, where the client sends a message to which the server responds (if appropriate). However, there are situations in which a client wants to receive data on a periodic or on-change basis, such as for sensor data, and having to send a request every time that data is desired adds additional network traffic. At the extreme, this additional network traffic could impact performance and safety. As such, when the Events service is supported on a server, a client can request for messages to be sent to it periodically or on an on-change basis.
Event Timeout
One potential issue with sending messages to a client without a triggering request is that if the client goes away unexpectedly, the server will continue to try to send messages which could impact performance and safety. To prevent this, the Events service supports the ability for a server to specify a timeout for event subscriptions. If clients doe not re-subscribe to an event before the timeout expires, the server will cancel the event and stop sending messages to that client.