QNetworkAccessManager can not post multipart data

[kiryu]

I use QNetworkAccessManager to upload file to my server. But sometimes QNetworkAccessManager did not post any data at all according to wireshark monitor. My code is as follows:
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QHttpMultiPart *pMultiPart = new QHttpMultiPart(QHttpMultiPart::FormDataType);
for (QHash<QString, QPair<GString, GString>>::const_iterator iter = fileList.cbegin(); iter != fileList.cend(); ++iter)
{
QHttpPart oFilePart;
oFilePart.setHeader(QNetworkRequest::LocationHeader, QVariant(iter.value().first));
oFilePart.setHeader(QNetworkRequest::ContentDispositionHeader,
GString("form-data; name="file"; filename="%1"").arg(iter.key()));
oFilePart.setHeader(QNetworkRequest::ContentTypeHeader, "application/octet-stream");
QFile *pfile = new QFile(iter.key());
pfile->open(QIODevice::ReadOnly);
oFilePart.setBodyDevice(pfile);
pfile->setParent(pMultiPart);
pMultiPart->append(oFilePart);
}

QUrl oURL(m_sURL);
QNetworkRequest oRequest(oURL);
QNetworkReply *pReply = m_pNetWorkAccessManager->post(oRequest, pMultiPart);
pMultiPart->setParent(pReply);
if (waitForReplyFinished(pReply))
{
    bool bRet = pReply->error() == QNetworkReply::NoError;
    pReply->deleteLater();
    return bRet;
}
else
{
    return false;
}

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