'Initialises a ProtocolMessage object.'

def __init__(self, payload='', paddingLen=0, flags=const.FLAG_PAYLOAD):

    payloadLen = len(payload)
    if ((payloadLen + paddingLen) > const.MPU):
        raise base.PluggableTransportError('No    overly    long    messages.')
    self.totalLen = (payloadLen + paddingLen)
    self.payloadLen = payloadLen
    self.payload = payload
    self.flags = flags
