Download multiple files from Ftp issue

Cobra91151

Hi! I want to download some files from my ftp server. The problem is, that only the last one has data, others 0 sized or it crashes when close QFile as a pointer.

My code:

QFtp *ftp = new QFtp(this);
ftp->connectToHost(FTP_HOST, FTP_PORT);
ftp->login(FTP_USERNAME, FTP_PASSWORD);
QFile *reportFile = nullptr;

connect(ftp, &QFtp::listInfo, [this](const QUrlInfo &ftpUrlInfo) {
        if (ftpUrlInfo.isFile()) {
            reportFile = new QFile("some local path" + ftpUrlInfo.name());
            reportFile->open(QIODevice::WriteOnly);
            ftp->get("some ftp path" + ftpUrlInfo.name(), reportFile, QFtp::Binary);
        }
    });
connect(ftp, &QFtp::done, [this]() {
        qDebug() << "DONE!";
        ftp->close();
        ftp->deleteLater();
    });
    connect(ftp, &QFtp::commandFinished, [this]() {
        qDebug() << "COMMAND FINISHED!";

            if (reportFile != nullptr) {
                reportFile.close();
                reportFile->deleteLater();
            }
    });

ftp->list("ftp path to dir");

So, it should download the file, close it and deleteLater for all files in the ftp directory. Any ideas how to do it? Thanks.

JonB

@Cobra91151
How are you waiting for one file's get() to finish, before you set off the next one? You are reusing the same reportFile variable over & over, while it is still servicing previous file get()s? Hence you only get the final file, and the crashes when one file's reportFile.close(); closes/deletes the reportFile from a different file!? (Put a qDebug() in the first connect(), not just the other two.)

Either wait if you want to do one-at-a-time synchronously, or you need to maintain multiple different reportFiles to do them all asynchronously.

Cobra91151

@JonB

Ok. I will change code and reply. Thanks.

Cobra91151

I have tried to use QList<QFile*> and append the files when they are listing, and then loop it, and when command get() finished, close and deleteLater() the file, now it doesn't crash when use QFile as a pointer but all files are 0 sized.

if (ftp->currentCommand() == QFtp::Get) {
     qDebug() << "GET FINISHED!";
     reportFile->close();
     reportFile->deleteLater();
}

I think that here is better to use QQueue and proceed the file one by one.

mrjj

Hi
Did you replace reportFile with access to the QList<QFile*>
so each invocation works on the right QFile?
Should work just as fine as one.
But yeah if 1 download works, than using a queue should be ok easy.

Cobra91151

@mrjj

Yes, 1 file downloads works. The problem with collection of files. I'm currently working to fix it.

mrjj

@Cobra91151
Ok if concurrent download is not a must have, one by one should be fairly
easy to implement if 1 download already works.

It sounds like you did it correctly with QList<QFile*> but you never showed
full code after the change so its unclear if just a normal bug-ish or
something with QFtp .
Also the shown connect(ftp, &QFtp::done ) would delete the ftp on first file finished
but assume you fixed that also ?

Cobra91151

@mrjj

I will post more code soon. Yes, I have fixed it by creating closeFtp function and connect to it when it finished, so I just need to read more docs on the QQueue and fix the issue with the files.

void Test::closeFtp()
{
    qDebug() << "FTP CLOSED";
    ftp->close();
    ftp->deleteLater();
    emit finished();
}

I will reply later. Thanks.

Cobra91151

@mrjj

Hi! I have finally fixed it!

My code:

QQueue<QFile*> reportQueue; //initialize the queue

connect(ftp, &QFtp::listInfo, [this](const QUrlInfo &ftpUrlInfo) {
        if (ftpUrlInfo.isFile()) {
            reportQueue.append(new QFile("local path" + "\\" + ftpUrlInfo.name()));
        }
    });
    connect(ftp, &QFtp::done, [this]() {
        emit reportsDataFinished();
    });
    connect(ftp, &QFtp::commandFinished, [this]() {
        if (ftp->currentCommand() == QFtp::List) {
            proceedDownload();
        } else if (ftp->currentCommand() == QFtp::Get) {
            reportFile->close();
            reportFile->deleteLater();
            proceedDownload();
        }
    });

    if (ftp->error() == QFtp::NotConnected) {
        emit ftpReportError(ftp->error());
    } else {
        ftp->list("ftp path to the dir");
    }

void Test::proceedDownload()
{
    if (!reportQueue.isEmpty()) {
        reportFile = reportQueue.dequeue();
        reportFile->open(QIODevice::WriteOnly);
        QFileInfo ftpFileInfo(reportFile->fileName());
        ftp->get("ftp path to file" + "/" + ftpFileInfo.fileName(), reportFile, QFtp::Binary);
    }
}

I added the files to the QQueue, when ftp list command has been finished, I use function proceedDownload(). In the function, I dequeue() the queue to the reportFile and proceed with ftp get() function. When get ftp command finishes, I close and delete the file from memory, and again call the proceedDownload(). So the the whole process goes again until the queue is empty. I use emit reportsDataFinished(); signal in the connection to the slot closeFtp() where ftp closes and deleteLater() frees the resources. All files downloads well. Thank you.

mrjj

Super :)
Seems pretty compact.