private function validate_client($client)
    {
        if (!isset($client->{"name"}))
            throw new \Exception("'client' has no 'name'!");
        if (!isset($client->{"queues"}))
            throw new \Exception("'client' has no 'queues'!");
        if (!isset($client->{"queues"}->{'input'}))
            throw new \Exception("'client' has no 'input' queue!");
        if (!isset($client->{"queues"}->{'output'}))
            throw new \Exception("'client' has no 'output' queue !");
    }