Checks if the client has sent a ready message.
        A ready message causes ``send()`` to be called on the
        ``parent end`` of the pipe.

        Clients need to ensure that the pipe assigned to ``self.pipe`` is
        the ``parent end`` of a pipe.

        This ensures completion of the underlying websocket connection
        and can be used to synchronize parallel senders.

def received_message(self, message):
        '''
        Checks if the client has sent a ready message.
        A ready message causes ``send()`` to be called on the
        ``parent end`` of the pipe.

        Clients need to ensure that the pipe assigned to ``self.pipe`` is
        the ``parent end`` of a pipe.

        This ensures completion of the underlying websocket connection
        and can be used to synchronize parallel senders.
        '''
        if message.data.decode('utf-8') == 'websocket client ready':
            self.pipe.send(message)
        self.send('server received message', False)