title: Spring Integration and TCP server socket - how can I send a message to a client?
body: <p>I'm trying to create a server in Spring that's listening on a TCP port and accepts connections.
  I know how to route incoming requests to my service, and it can respond to those.
  However I would like to send messages to certain clients without any request received. For example, sometimes I have to inform a client about that it has got a message.</p>
  
  <p>To do this, I think I need a way to identify the clients, e.g. by letting them log in. Is there a way to have a "session" object for each active connection in which I can store login data?</p>
  
  <p>How could I send a message to a client which has logged in with username X?</p>
  
  <p>Is this possible in Spring at all?</p>