详解QT使用http通信的同步和异步

	QUrl url(myurl);
    QNetworkReply *reply = quitmanager->get(QNetworkRequest(QUrl(url)));
    QEventLoop eventLoop;
    connect(quitmanager, SIGNAL(finished(QNetworkReply*)), &eventLoop, SLOT(quit()));
    eventLoop.exec();       //block until finish

    //reply->readall()
    reply->deleteLater();
    reply = nullptr;

    return true;

    QNetworkAccessManager *manager = new QNetworkAccessManager;
    QNetworkRequest *request = new QNetworkRequest;
    connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(finishedSlot(QNetworkReply*)));//绑定槽函数
    //get  post请求二选一
    QUrl url(urlHead+"exam_start/"+studentId);
    request->setUrl(url);
    manager->get(*request);//发送get请求

​​​​QByteArray postData = document.toJson(QJsonDocument::Compact);
    request->setUrl(url);
    request->setHeader(QNetworkRequest::ContentTypeHeader,QVariant("application/json"));
    manager->post(*request, postData);//发送post请求

void MainWindow::finishedSlot(QNetworkReply *reply)
{
    qDebug() << "进入函数: " <<  __FUNCTION__;

    QString json = reply->readAll();//这个返回的JSON包所携带的所有信息
    QJsonParseError jsonerror;
    QJsonDocument doc = QJsonDocument::fromJson(json.toUtf8(), &jsonerror);

​​​​​​​    if (!doc.isNull() && jsonerror.error == QJsonParseError::NoError)
    {
        QJsonObject object = doc.object();
        if(object.contains("type"))
        {
            switch (object.value("type").toInt())
            {
                case 1:parseLogJason(object);break;
                case 2:parseParameterJason(object);break;
                case 3:parseExamStartJason(object);break;
                case 4:parseExamEndJason(object);break;
                default:return;
            }
        }
    }
}

     QNetworkAccessManager* manager6 = new QNetworkAccessManager(this);
    // 准备工作 - 初始化一个QNetworkRequest
    QNetworkRequest res6;
     //设置头 - 浏览器
    res6.setHeader(QNetworkRequest::UserAgentHeader,
                  "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Safari/537.36");
    res6.setUrl(QUrl("http://" + IP + "/version"));
    QNetworkReply* reply6 = manager6->get(res6);
    reply6->attribute(QNetworkRequest::HttpStatusCodeAttribute);
    reply6->attribute(QNetworkRequest::RedirectionTargetAttribute);


    // 读服务器回写的数据
    connect(reply6, &QNetworkReply::readyRead, this, [=]()
    {
        //QVariant str = reply6->header(QNetworkRequest::LocationHeader);
        QByteArray data = reply6->readAll();
        //qDebug() << "version  "<< data ;
        QString str = QString(data);
        int pos = str.indexOf('-');
        version[node_id] =  str.mid(pos + 3, 2) + "."+ str.mid(0, pos ) ;
        reply6->abort();
        reply6->close();
        reply6->deleteLater();
        manager6->deleteLater();
    });