Qt QNetworkAccessManager为什么我不能在同一主线程中并行发送多个http请求

我刚刚注意到，当我尝试发送http请求，而已经有http请求在后台进行，其中一个停止等待，直到前一个结束。它们都使用自己的qnetworkaccessmanager。有人能解释一下为什么会这样吗?

我一定是在这里做错了什么我不知道，这里有一些代码。
有两个HTTP post函数，第一个是简单的post，每5秒调用一次第二个是并行调用的文件上传post函数。
当我调用文件上传的第一个停止，直到文件上传完成，并继续这是来自Qt与我的干预。这是使用单个QNetworkAccessManager

    //Init in the class contractor
     networkManager = new QNetworkAccessManager(this); 
     connect(networkManager,SIGNAL(sslErrors(QNetworkReply*,QList<QSslError>)), this, SLOT(on_sslErr(QNetworkReply*,QList<QSslError>)));

    //-----------------------------------------------------\
    //this is upload file code , its taking time untill it finish working great
    PostImageRequest( QString& Response,
                                    QMap<QString,QString> paramsToPostMap,
                                    QString& BaseUrl,
                                    QString imageFullPath,
                                    int iTimeOutInterval)

    QByteArray imageFormat = QImageReader::imageFormat(imageFullPath);
    QString imageMimeType(imageFormat);
    QNetworkRequest request;
    QUrl params;
    QMapIterator<QString,QString> i(paramsToPostMap);
    while (i.hasNext()) {
        i.next();
        addField(i.key(),i.value());
    }
      addFile("file",imageFullPath,imageMimeType);
      QString crlf="rn";
      qsrand(QDateTime::currentDateTime().toTime_t());
      QString b=QVariant(qrand()).toString()+QVariant(qrand()).toString()+QVariant(qrand()).toString();
      QString boundary="---------------------------"+b;
      QString endBoundary=crlf+"--"+boundary+"--"+crlf;
      QString contentType="multipart/form-data; boundary="+boundary;
      boundary="--"+boundary+crlf;
      QByteArray bond=boundary.toAscii();
      QByteArray send;
      bool first=true;
      for (int i=0; i<fieldNames.size(); i++) {
        send.append(bond);
        if (first) {
          boundary=crlf+boundary;
          bond=boundary.toAscii();
          first=false;
        }
        send.append(QString("Content-Disposition: form-data; name=""+fieldNames.at(i)+"""+crlf).toAscii());
        if (encodingS=="utf-8") send.append(QString("Content-Transfer-Encoding: 8bit"+crlf).toAscii());
        send.append(crlf.toAscii());
        send.append(strToEnc(fieldValues.at(i)));
      }
      for (int i=0; i<files.size(); i++) {
        send.append(bond);
        send.append(QString("Content-Disposition: form-data; name=""+fileFieldNames.at(i)+""; filename=""+fileNames.at(i)+"""+crlf).toAscii());
        send.append(QString("Content-Type: "+fileMimes.at(i)+crlf+crlf).toAscii());
        send.append(files.at(i));  
      }
      send.append(endBoundary.toAscii());
      fieldNames.clear();
      fieldValues.clear();
      fileFieldNames.clear();
      fileNames.clear();
      fileMimes.clear();
      files.clear();
     request.setHeader(QNetworkRequest::ContentTypeHeader, contentType.toAscii());
 request.setHeader(QNetworkRequest::ContentLengthHeader, QVariant(send.size()).toString());
     request.setUrl(BaseUrl);

     if(iTimeOutInterval != -1)
     {
         QEventLoop loop2;
         QTimer::singleShot(iTimeOutInterval, &loop2, SLOT(quit()) );
         loop2.exec();
 }
     QEventLoop loop;
     QNetworkReply *reply = networkManager->post(request,send);
     connect(reply, SIGNAL(uploadProgress(qint64,qint64)), this,SLOT(SetProgress(qint64,qint64)));
     connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
 loop.exec();       
     //return response 
     QNetworkReply::NetworkError networkError = reply->error();
     HandleNetworkError(networkError); 
     Response.clear();
     QByteArray data=reply->readAll();
     Response.append(data);
     //delete reply;
     reply->deleteLater();
    //--------------------------------------------------------------------------------\
//this is the post function that invoket every 5 secound
    PostRequest(QString& Response,
                            QMap<QString,QString> paramsToPostMap,
                            QString& BaseUrl,
                            int iTimeOutInterval)

     QNetworkRequest request;
     QUrl params;
     QMapIterator<QString,QString> i(paramsToPostMap);
     while (i.hasNext()) {
        i.next();
        params.addQueryItem(i.key(),i.value());
     }
     request.setUrl(BaseUrl);
     QByteArray postArgs;
     postArgs = params.encodedQuery();
     if(iTimeOutInterval != -1)
     {
         QEventLoop loop2;
         QTimer::singleShot(iTimeOutInterval, &loop2, SLOT(quit()) );
         loop2.exec();
 }
     QEventLoop loop;
     QNetworkReply *reply = networkManager->post(request,postArgs);
     connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
 loop.exec();       
     //return response 
     QNetworkReply::NetworkError networkError = reply->error();
     HandleNetworkError(networkError); 
     Response.clear();
     QByteArray data=reply->readAll();
     Response.append(data);

     //delete reply;
     reply->deleteLater();