How to send information from server to the client?

The terms 'Client' and 'Server' are used according to their role in the request/response model. Client sends the Request, and the server provides a response. So the server is not able to send a request to the client. This does not mean that a machine acting as a server will not be able to intitiate a request, rather it will behave as a client if it does so.

It is not a good practice to send information from a component in the middle-tier to the presentation layer, since it violates the multi/tier encapsulation, that is, the business tier should not know about the presentation tier. If you do so, a minor change in the user interface will result in a change in the middle-tier component, which may be used by many users.

Also it is not a good security practice to send information from server to the client.

However, if you are serious, it is possible to do it using call-back functions. Refer to the references discussing this subject, or mail me to send a little sample application.