Java chat - connection just on request

I just programmed a Java Server-Client Chat (with multiple clients) where they log in, chat and log out. The socket is always started and I listen in a loop.

Now I have to program 开发者_Go百科this kind of chat where the connection isn't always open, so the the connection just stars "on request" (when someone sends a message).

How do I do this? Could you give me some keywords which I should google?

If you want to create a Server and Client that does not have a Open Connection (Correct me If I am wrong) you will have to Open and close the connection manually. As these "connections" represent Streams across the network.

Another Option you can consider is maybe using UDP, but this does not close and open a connection on request it only removes the overhead of TCP and it's reliability features.

From the Datagram Lesson on Oracle.com:

Some applications that you write to communicate over the network will not require the reliable, point-to-point channel provided by TCP. Rather, your applications might benefit from a mode of communication that delivers independent packages of information whose arrival and order of arrival are not guaranteed.