def subscribe(dest, ack='auto'):
    """STOMP subscribe command.

    dest:
        This is the channel we wish to subscribe to

    ack: 'auto' | 'client'
        If the ack is set to client, then messages received will
        have to have an acknowledge as a reply. Otherwise the server
        will assume delivery failure.

    """
    return 'SUBSCRIBE\ndestination: %s\nack: %s\n\n\x00\n' % (dest, ack)
