QNetworkInformation Class

#include <QCoreApplication>
#include <QNetworkInformation>
#include <QDebug>

voidonReachabilityChanged(QNetworkInformation::Reachability reachability) {
    switch(reachability) {
    caseQNetworkInformation::Reachability::Unknown:
        qDebug() << "Network reachability is unknown.";
       break;
    caseQNetworkInformation::到達可能性::接続切れ:
        qDebug() << "Network is disconnected.";
       break;
    caseQNetworkInformation::到達可能性::ローカル:
        qDebug() << "Network is locally reachable.";
       break;
    caseQNetworkInformation::到達可能性::サイト:
        qDebug() << "Network can reach the site.";
       break;
    caseQNetworkInformation::Reachability::Online:
        qDebug() << "Network is online.";
       break;
    }
}

intmain(intargc, char *argv[]) {
    QCoreApplication a(argc,argv);

    // QNetworkInformation がサポートされているか確認
    if(!QNetworkInformation::loadDefaultBackend()) {
        qWarning() << "QNetworkInformation is not supported on this platform or backend.";
       return 1;
    }

    QNetworkInformation*netInfo=QNetworkInformation::instance();

    // reachabilityChangedシグナルに接続する
    QObject::connect(netInfo, &QNetworkInformation::reachabilityChanged,
                     &onReachabilityChanged);

    // 初期状態を出力
    onReachabilityChanged(netInfo->reachability());

    returna.exec();
}

// IPアドレスが「ローカル」であるかどうかを判定する簡単なヘルパー関数
boolisLocalAddress(constQHostAddress&address)
{
    returnaddress.isInSubnet(QHostAddress("192.168.0.0"), 16)||
           address.isInSubnet(QHostAddress("10.0.0.0"), 8)     ||
           address.isInSubnet(QHostAddress("172.16.0.0"), 12)  ||
           address.isLoopback();
}

intmain(intargc, char *argv[])
{
    ...
    // 対象のIPアドレス（デフォルト：Google DNS）
    QString targetIpStr=argc> 1 ?argv[1]:"8.8.8.8";
    QHostAddress targetIp(targetIpStr);

    if(targetIp.isNull()) {
        qWarning() << "Invalid IP address:" << targetIpStr;
       return 1;
    }

    // ターゲットに対してどのレベルの到達可能性が必要かを決定する
    QNetworkInformation::Reachability requiredReachability=
        isLocalAddress(targetIp)
            ?QNetworkInformation::Reachability::Local
            : QNetworkInformation::Reachability::Online;

    // システムが報告している現在の到達可能性を取得する
    QNetworkInformation::Reachability currentReachability= networkInfo->reachability();

    qDebug() << "Target IP:" << targetIp.toString();
    qDebug() << "Target is considered"
            <<(isLocalAddress(targetIp)? "local/site.":"external/online.");
    qDebug() << "Required reachability level:" << requiredReachability;
    qDebug() << "Current reachability:" << currentReachability;

   if(currentReachability<requiredReachability) {
        qWarning() << "Current network state may not allow reaching the target address.";
    }else{
        qDebug() << "Target may be reachable based on current network state.";
    }
    ...