protected function disconnect()
    {
        $this->log('closing sockets ... ', Net_Notifier_Logger::VERBOSITY_ALL);

        foreach ($this->clients as $client) {
            $client->startClose(
                Net_Notifier_WebSocket_Connection::CLOSE_GOING_AWAY,
                'Server shutting down.'
            );
        }

        $this->clients = array();
        $this->socket  = null;

        $this->log('done' . PHP_EOL, Net_Notifier_Logger::VERBOSITY_ALL, false);

        $this->connected = false;
    }