Creating an HTTP network request in Qt

Article Metadata

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Tested with

Devices(s): Nokia 5800 XpressMusic

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Compatibility

Platform(s): S60 3rd Edition, FP1, FP2
S60 5th Edition

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Article

Keywords: QNetworkAccessManager, QUrl, QNetworkReply, QNetworkRequest

Created: tepaa (04 Jun 2009)

Last edited: hamishwillee (11 Oct 2012)

Overview

This code snippet demonstrates how to use QNetworkAccessManager for sending an HTTP request.

Note: In order to use this code, you need to have Qt installed on your platform.

Header

#include <QNetworkAccessManager>
#include <QUrl>
#include <QNetworkRequest>
#include <QNetworkReply>
 
QNetworkAccessManager* nam;

Source

Create QNetworkAccessManager and start listening for its finished signal.

nam = new QNetworkAccessManager(this);
QObject::connect(nam, SIGNAL(finished(QNetworkReply*)),
         this, SLOT(finishedSlot(QNetworkReply*)));

HTTP GET request:

QUrl url("http://www.forum.nokia.wiki");
QNetworkReply* reply = nam->get(QNetworkRequest(url));
// NOTE: Store QNetworkReply pointer (maybe into caller). 
// When this HTTP request is finished you will receive this same 
// QNetworkReply as response parameter. 
// By the QNetworkReply pointer you can identify request and response.

When the QNetworkAccessManager::finished signal is received, the HTTP request is completed.

void MyHttpEngine::finishedSlot(QNetworkReply* reply)
{   
    // Reading attributes of the reply
    // e.g. the HTTP status code
    QVariant statusCodeV = 
    reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);
    // Or the target URL if it was a redirect:
    QVariant redirectionTargetUrl =
    reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
    // see CS001432 on how to handle this
 
    // no error received?
    if (reply->error() == QNetworkReply::NoError)
    {
        // read data from QNetworkReply here
 
        // Example 1: Creating QImage from the reply
        QImageReader imageReader(reply);
        QImage pic = imageReader.read();
 
        // Example 2: Reading bytes form the reply
        QByteArray bytes = reply.readAll();  // bytes
        QString string(bytes); // string
    }
    // Some http error received
    else
    {
        // handle errors here
    }
 
    // We receive ownership of the reply object
    // and therefore need to handle deletion.
    delete reply;
}

See also

• For more information about QNetworkAccessManager, see QNetworkAccessManager Class Reference
• Handling an HTTP redirect with QNetworkAccessManager

Postconditions

An HTTP response is received.