QNetworkRequest Redirect doesn't seem to work in Qt6

hbatalha

In Qt5 this works great:

auto manager = new QNetworkAccessManager();

QObject::connect(manager, &QNetworkAccessManager::finished,
        [&](QNetworkReply* repl) {
    qDebug() << repl->readAll();
});
QNetworkRequest req(QUrl("http://www.dropbox.com/s/ehoawgm89yz6pib/version.txt?raw=1")); 
req.setAttribute(QNetworkRequest::FollowRedirectsAttribute, true);
req.setMaximumRedirectsAllowed(3);
QNetworkReply* reply = manager->get(req);

But Qt6 brought changes to Qt Network. In the Redirect policies it states:

In Qt 6, the default redirect policy has changed from manual to QNetworkRequest::NoLessSafeRedirectPolicy. If your application relies on manual redirect handling (it connects its slot to the QNetworkReply::redirected signal), you have to explicitly set this policy when creating a request:
request.setAttribute(QNetworkRequest::RedirectPolicyAttribute, QNetworkRequest::ManualRedirectPolicy);

In the doc it says Network Access API does follow redirections by default, but it doesn't work. This what I have tried:

QNetworkRequest req(QUrl("http://www.dropbox.com/s/ehoawgm89yz6pib/version.txt?raw=1"));
req.setAttribute(QNetworkRequest::RedirectPolicyAttribute, QNetworkRequest::NoLessSafeRedirectPolicy);
eq.setMaximumRedirectsAllowed(3);

Also when using Qt5 it warns that QNetworkRequest::FollowRedirectsAttribute is deprecated and that I should use QNetworkRequest::RedirectPolicyAttribute(this compiles in Qt6 but doesn't download anything, it works in Qt5)

SGaist

Hi,

Did you connect the various error signals to see what happens on that front ?

hbatalha

@SGaist Nope, I will do that and get back to you

hbatalha

This post is deleted!

hbatalha

@SGaist @SGaist With this code:

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QNetworkAccessManager* net = new QNetworkAccessManager;

    auto reply = net->get(QNetworkRequest(QUrl("https://www.dropbox.com/s/zqbxgw4owoteas0/version.txt?dl=1")));

    QObject::connect(reply, &QNetworkReply::downloadProgress, [](qint64 received, qint64 total)
    {
        qDebug() << received << " of " << total;
    });

    QObject::connect(net, &QNetworkAccessManager::finished, [](QNetworkReply* reply)
    {
        if(! reply->error())
        {
            QByteArray data = reply->readAll();

            QString dest_file = "D:/Desktop/test.txt";

            QFile file(dest_file);

            if(QFile::exists(dest_file))
                QFile::remove(dest_file);

            if( ! file.open(QIODevice::ReadWrite | QIODevice::Truncate))
                qDebug () << "Could not save the file";

            file.write(data);
            file.close();
        }
        else
            qDebug() << "ERROR: " << reply->errorString();

        reply->deleteLater();
    });

    return a.exec();
}

I get the following error:

ERROR: "Host not found"

I will g search to see what comes up

eyllanesc

@hbatalha I just tested your code adding request.setAttribute(QNetworkRequest::RedirectPolicyAttribute, QNetworkRequest::ManualRedirectPolicy); and it works fine.

#include <QCoreApplication>
#include <QFile>
#include <QNetworkAccessManager>
#include <QNetworkReply>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QNetworkAccessManager net;

    QNetworkRequest request(QUrl("https://www.dropbox.com/s/zqbxgw4owoteas0/version.txt?dl=1"));
    request.setAttribute(QNetworkRequest::RedirectPolicyAttribute, QNetworkRequest::ManualRedirectPolicy);

    QNetworkReply *reply = net.get(request);

    QObject::connect(reply, &QNetworkReply::downloadProgress, [](qint64 received, qint64 total)
    {
        qDebug() << received << " of " << total;
    });

    QObject::connect(&net, &QNetworkAccessManager::finished, [](QNetworkReply* reply)
    {
        if(! reply->error())
        {
            QByteArray data = reply->readAll();

            QString dest_file = "test.txt";

            QFile file(dest_file);

            if(QFile::exists(dest_file))
                QFile::remove(dest_file);

            if( ! file.open(QIODevice::ReadWrite | QIODevice::Truncate))
                qDebug () << "Could not save the file";

            file.write(data);
            file.close();
        }
        else
            qDebug() << "ERROR: " << reply->errorString();

        reply->deleteLater();
    });

    return a.exec();
}

Output

135  of  -1
135  of  135

SGaist

So it's all good ?

hbatalha

@eyllanesc From the OP :
But Qt6 brought changes to Qt Network. In the Redirect policies it states:

In Qt 6, the default redirect policy has changed from manual to QNetworkRequest::NoLessSafeRedirectPolicy. If your application relies on manual redirect handling (it connects its slot to the QNetworkReply::redirected signal), you have to explicitly set this policy when creating a request:
request.setAttribute(QNetworkRequest::RedirectPolicyAttribute, QNetworkRequest::ManualRedirectPolicy);

With that option and without a manual redirect handling what it does is write the text below to file:

301 Moved Permanently

The resource has been moved to /s/dl/zqbxgw4owoteas0/version.txt;

you should be redirected automatically.

I don't want to to create a slot to handle redirect as it should work without but I tried either way and the signal for redirect doesn't to be emitted or I am writing the code wrong:

req.setAttribute(QNetworkRequest::RedirectPolicyAttribute, QNetworkRequest::ManualRedirectPolicy);

    QNetworkReply* reply;
    reply = net->get(req);

    QObject::connect(reply, &QNetworkReply::redirected, [] (QUrl url)
    {
        qDebug() << "HERE"; // never called
        
        redirect(url); //void redirect(QUrl url)
    });

hbatalha

@hbatalha Update:

I've upgraded Qt to version 6.1.2 MinGW 64-bit. The redirect seems to be working as I was able to download GDrive direct link that had redirect but I can't download a dropbox file, I have tested the link with pure c curl and it works great but with QNetworkAccessManager I keep getting the 'Host not found' error though.

I am looking for more links with redirects to tests. I update any news here.