Called when the request handler is unregistered, or the session is closed.
Notification of a contextual error related to this handler. This is
analogous to an Error being thrown. Situations in which
onError is called include the session being closed before the
handler is registered, a communication timeout, or a problem with the
provided parameters. No further calls will be made to this handler.
the error
Called to indicate a request has been received.
The request that was received
Context object that provides the session id (session that sent the request), path and session properties
The responder to dispatch a response back to the requester
Interface which specifies a request handler to receive request notifications.
Session.messages.RequestHandler