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Thread: Unable to download file at URL, works fine in Chromium/Firefox/cURL

  1. #1
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    Default Unable to download file at URL, works fine in Chromium/Firefox/cURL

    I'm trying to download a private Google Calendar using a QNetworkAccessManager. Google offers an iCal export function through URLs similar to https://www.google.com/calendar/ical/[MY E-MAIL ADDRESS]/private-[RANDOM STRING OF LETTERS AND NUMBERS]/basic.ics. This calendar can be accessed by other applications through this URL, as described in Google Calendar's documentation.

    I use the following code to download a file from a given URL.

    Qt Code:
    1. // _naMgr is a function member of type QNetworkAccessManager
    2. connect(&_naMgr, SIGNAL(finished(QNetworkReply*)), this, SLOT(buildCalendar(QNetworkReply*)));
    3. _naMgr.get(QNetworkRequest(_url));
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    Qt Code:
    1. void Calendar::buildCalendar(QNetworkReply* reply) {
    2. _content = reply->readAll();
    3.  
    4. // TODO: debug
    5. msg.setText(_content);
    6. msg.exec();
    7. }
    To copy to clipboard, switch view to plain text mode 

    So then I tried downloading my private calendar through the URL provided by Google. This works fine in Chromium, vanilla Firefox (i.e. no prior session data or cookies) and cURL. However, when I try to access the URL through my little program I am served with this Dutch error page. (It says "Feed Processing Error".)

    Is there something specific in Qt's way of handling URLs that may cause Google's server to respond differently?

  2. #2
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    Default Re: Unable to download file at URL, works fine in Chromium/Firefox/cURL

    No, Qt does the right thing with URLs.

    Since you don't show us how you construct your URL it is hard for any help to be offered.

  3. #3
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    Default Re: Unable to download file at URL, works fine in Chromium/Firefox/cURL

    You can use something like etherpeek or wireshark to determine the differences between your code and what Firefox/etc uses.

    You have not provided sufficient code for us to offer any other help.

  4. #4
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    Default Re: Unable to download file at URL, works fine in Chromium/Firefox/cURL

    I've created a new calendar on which I can reproduce the same behavior.

    https://www.google.com/calendar/ical...ee3c/basic.ics

  5. #5
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    Default Re: Unable to download file at URL, works fine in Chromium/Firefox/cURL

    Quote Originally Posted by squidge View Post
    You have not provided sufficient code for us to offer any other help.
    I've narrowed it down to this...

    Qt Code:
    1. // --- MAIN.CPP ---
    2. #include <QtGui/QApplication>
    3. #include "mainwindow.h"
    4.  
    5. int main(int argc, char *argv[])
    6. {
    7. QApplication a(argc, argv);
    8. MainWindow w;
    9. w.show();
    10.  
    11. return a.exec();
    12. }
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    Qt Code:
    1. // --- MAINWINDOW.H ---
    2.  
    3. #ifndef MAINWINDOW_H
    4. #define MAINWINDOW_H
    5.  
    6. #include <QtGui/QMainWindow>
    7. #include <QNetworkAccessManager>
    8.  
    9. class QNetworkReply;
    10.  
    11. class MainWindow : public QMainWindow
    12. {
    13. Q_OBJECT
    14.  
    15. public:
    16. MainWindow(QWidget *parent = 0);
    17.  
    18. private:
    19. QNetworkAccessManager _naMgr;
    20. private slots:
    21. void downloadedURL(QNetworkReply*);
    22. };
    23.  
    24. #endif // MAINWINDOW_H
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    Qt Code:
    1. // --- MAINWINDOW.CPP ---
    2.  
    3. #include "mainwindow.h"
    4.  
    5. #include <QMessageBox>
    6. #include <QNetworkReply>
    7. #include <QNetworkRequest>
    8.  
    9. MainWindow::MainWindow(QWidget *parent)
    10. : QMainWindow(parent)
    11. {
    12. connect(&_naMgr, SIGNAL(finished(QNetworkReply*)), this, SLOT(downloadedURL(QNetworkReply*)));
    13. _naMgr.get(QNetworkRequest(QUrl("https://www.google.com/calendar/ical/38e7dvaj3mnlrlb2kcsuamugcs%40group.calendar.google.com/private-4c87c506a44134d2f6a0f0be1d82ee3c/basic.ics")));
    14. }
    15.  
    16. void MainWindow::downloadedURL(QNetworkReply* reply) {
    17. QString content = reply->readAll();
    18.  
    19. msg.setText(content);
    20. msg.exec();
    21. }
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  6. #6
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    Default Re: Unable to download file at URL, works fine in Chromium/Firefox/cURL

    So your passing an encoded string to a constructor (QUrl) which expects a non-encoded string? So whats probably happening is that QUrl is then confusing the web server by encoding your encodings.

    Try changing your URL to human readable format instead. Eg. replace things like %40 with the actual character (which I think is @)

  7. The following user says thank you to squidge for this useful post:

    blooglet (13th September 2011)

  8. #7
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    Default Re: Unable to download file at URL, works fine in Chromium/Firefox/cURL

    i see your are using https you might be getting SSL error probably SSL Handshake Error.

    Try using
    Qt Code:
    1. reply->ignoreSslErrors();
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    Note that calling this function without restraint may pose a security risk for your application. Use it with care.

    Read document here

  9. #8
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    Default Re: Unable to download file at URL, works fine in Chromium/Firefox/cURL

    Quote Originally Posted by squidge View Post
    So your passing an encoded string to a constructor (QUrl) which expects a non-encoded string? So whats probably happening is that QUrl is then confusing the web server by encoding your encodings.

    Try changing your URL to human readable format instead. Eg. replace things like %40 with the actual character (which I think is @)
    You're right, it works if I apply QUrl::fromEncoded to the encoded string first. Thanks!

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