How to detect internet connection state with Qt 5.4 on OS X Yosemite 10.10.3?

Question

I'm trying to check the internet connection state with Qt 5.4 on OS X Yosemite 10.10.3, but every time I run the code the result is connected, although I'm not connected to anything.

bool NetworkAccessManager::currentConnectivityStatus()
{
    QNetworkAccessManager *namanager = new QNetworkAccessManager(this);
    switch (namanager->networkAccessible()) {
    case QNetworkAccessManager::UnknownAccessibility:
        kdebug() << Q_FUNC_INFO << "QNetworkAccessManager::UnknownAccessibility";
        break;
    case QNetworkAccessManager::NotAccessible:
        kdebug() << Q_FUNC_INFO << "QNetworkAccessManager::NotAccessible";
        break;
    case QNetworkAccessManager::Accessible:
        kdebug() << Q_FUNC_INFO << "QNetworkAccessManager::Accessible";
        break;
    default:
        break;
    }

    QNetworkConfigurationManager manager;
        kdebug()<< Q_FUNC_INFO << " network connection " << manager.isOnline();

    QNetworkConfiguration cfg = manager.defaultConfiguration();
    QNetworkSession *session = new QNetworkSession(cfg);
    session->open();
    session->waitForOpened();

    if(session->isOpen())
    {
        switch (session->state()) {
        case QNetworkSession::Connected:
            kdebug() << Q_FUNC_INFO << "QNetworkSession::Connected";
            break;
        case QNetworkSession::Disconnected:
            kdebug() << Q_FUNC_INFO << "QNetworkSession::disconnect";
            break;
        default:
            break;
        }
    }
}

And here is the result for all the above when i disconnect everything

DEBUG 2015-04-25T16:00:59.560 bool NetworkAccessManager::currentConnectivityStatus() QNetworkAccessManager::Accessible 
DEBUG 2015-04-25T16:00:59.560 bool NetworkAccessManager::currentConnectivityStatus()  network connection OK  true 
DEBUG 2015-04-25T16:00:59.560 bool NetworkAccessManager::currentConnectivityStatus() QNetworkSession::Connected 

Answer 1

从C / C ++程序执行ping操作是如何ping外部服务器，实施此操作，如果ping则返回true，否则返回false。