gistfile1.scala

 val closeFuture = new Promise[Unit]
 val c = new ClientConnection {
   def remoteAddress: SocketAddress = null
   def localAddress: SocketAddress = null
   def onClose: Future[Unit] = closeFuture
   def close(deadline: Time): Future[Unit] = {
     closeFuture.setDone()
     closeFuture
  }
}