QNetworkAccessManager 实现ftp上传时，如果ftp服务器关闭了，QNetworkReply无响应，应如何捕获异常

[mct123]

部分代码：    

QNetworkRequest req(url);
    QNetworkReply *tmp = nam.put(req, data);
    if(tmp != NULL)
    {
        applog::LOGGER->Log(applog::kLogInfo, "LedDispatch::AsynchronousUploadLed %s - %s",info.ip.toUtf8().constData() ,data.constData());

        replyMap[info.ip] = tmp;
        connect(tmp, SIGNAL(finished()), this, SLOT(sendUpdateCmd()));//上传成功后，会再执行其他命令操作
        connect(tmp, SIGNAL(error(QNetworkReply::NetworkError)), this, SLOT(OnError(QNetworkReply::NetworkError)));
     }

现在这样，ftp服务器关闭了，测试发现程序两个槽函数都无响应