Using a technique called server push, the server can send messages back to the client.
Server push is particularly useful when the client needs to be notified of the completion of an asynchronous request.
The server can make both synchronous and asynchronous calls against client-side objects. The client handles server-side requests the same way the server handles client-side requests. Asynchronous requests against a particular client-side object are queued and processed after all synchronous requests.
To send a message to the client, the server needs to know which client-side object to send the message to. Therefore, the client must pass an object reference to the server. When the server receives the object reference, it creates a remote reference to the client-side object and calls one or more functions associated with this object. Function calls made against the remote reference are passed back over the wire to the client that contains the object.
To ensure that messages are actually sent to the client-side object, the client must not pass an autoinstantiated object to the server. Instead the client must pass a reference to an object that is created with the CREATE statement.
For more information
For an example of server push, see Example of server push.