'Check if it is possible to add a new server.'

def HandleServerAddCheck(self):

    if (not self.MASTER):
        return self._EmptyResponse(constants.RESPONSE_NOT_MASTER_SERVER)
    if (not self.MASTER.AllRegistered()):
        return self._EmptyResponse(constants.RESPONSE_DATA_SERVERS_UNREACHABLE)
    (addr, port) = self._UnpackNewServer()
    logging.info('Checking    new    server    %s:%d', addr, port)
    if self.MASTER.HasServer(addr, port):
        return self._EmptyResponse(constants.RESPONSE_EQUAL_DATA_SERVER)
    else:
        return self._EmptyResponse(constants.RESPONSE_OK)
