add Tcp.register overload with keepOpenOnPeerClosed parameter for Java usage

akka-actor/src/main/scala/akka/io/Tcp.scala

@@ -217,6 +217,7 @@ object TcpMessage {
            backlog: Int): Command = Bind(handler, endpoint, backlog, Nil)
 
   def register(handler: ActorRef): Command = Register(handler)
+  def register(handler: ActorRef, keepOpenOnPeerClosed: Boolean): Command = Register(handler, keepOpenOnPeerClosed)
   def unbind: Command = Unbind
 
   def close: Command = Close

akka-docs/rst/java/io.rst

@@ -442,7 +442,10 @@ successful, the listener will be notified with ``ConfirmedClosed``.
 ``Abort`` will immediately terminate the connection by sending a ``RST`` message to the remote endpoint. Pending
 writes will be not flushed. If the close is successful, the listener will be notified with ``Aborted``.
 
-``PeerClosed`` will be sent to the listener if the connection has been closed by the remote endpoint.
+``PeerClosed`` will be sent to the listener if the connection has been closed by the remote endpoint. Per default, the
+connection will then automatically be closed from this endpoint as well. To support half-closed connections set the
+``keepOpenOnPeerClosed`` member of the ``Register`` message to ``true`` in which case the connection stays open until
+it receives one of the above close commands.
 
 ``ErrorClosed`` will be sent to the listener whenever an error happened that forced the connection to be closed.