Handles readable client sockets. Calls the user modified handle_readable with
        the client socket as the only variable. If the handle_readable function returns
        true the client is again registered to the selector object otherwise the client
        is disconnected.

def _subthread_handle_readable(self, conn):
        """Handles readable client sockets. Calls the user modified handle_readable with
        the client socket as the only variable. If the handle_readable function returns
        true the client is again registered to the selector object otherwise the client
        is disconnected.
        """

        if self.handle_readable(conn):
            self.register(conn)
        else:
            self.disconnect(conn)