Socket using in a swing applet

I should made a server & client in Java,based on Swing and gui.I neeed to make somehow a socket that will go from the server to the client and from the client to the server, and will pass some kind of a string.I would like to have later a function that would do several things according to the string that would be in the socket.
For some reason I couldn't find a simple example for code that shows how it's done in a simple way.
Anyone has any simple example or can explain how is it being done?