private function processPubAck ($payload, $qos)
    {
        if( strlen($payload) < 2 ) {
            $this->debugMessage("Malformed PUBACK package received");
            return false;
        }

        $package_id = ( ord($payload{0}) << 8 ) + ord($payload{1});
        if( !isset($this->messageQueue[$package_id]) ) {
            $this->debugMessage("Received PUBACK for package we didn't sent?");
            return false;
        }

        unset( $this->messageQueue[$package_id] );
    }