Creating an HTTP network request in Qt using QNetworkAccessManager, QNetworkRequest, QNetworkReply
This article demonstrates how to prepare a HTTP request and to make use of the response.
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The example code demonstrates usage of QNetworkAccessManager, QNetworkRequest, QNetworkReply, QUrl and QSettings. HttpCommunicator and RawRequestUi are important classes which makes use of several Qt services to implement example application.
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UI for Entering the URL
RawRequestUi File:HttpConsole.zip class implements simple UI where user can enter URL such as http://beer.com RawRequestUi provides following user input elements
- Select type of request i.e. get, post, head, put or delete.
- Choose request body. Body can be taken from file or can be entered in text input field provided.
- Response area displays headers and response body received from HTTP request.
- Header area where user can insert HTTP header into the request.
Screen on Nokia 5800 using a Wifi Network
Screen on Nokia 5230 using a 3G Network
Creating Request
HttpCommunicator class makes use of QNetworkAccessManager, QNetworkRequest, QNetworkReply, QUrl to get its job done. QNetworkRequest::setUrl() is all you have to do to prepare a HTTP request. User entered headers are inserted using the API QNetworkRequest::setRawHeader().
Communicating with Server
QNetworkAccessManager encapsulates nitty-gritty of actual communication. QNetworkAccessManager has APIs such as get(), post(), deleteResource(), put(), head() to make HTTP request. HttpCommunicator hooks onto QNetworkAccessManager by providing slot for QNetworkAccessManager::finished().
Catching the Response
QNetworkReply makes the job easier by representing the network reply through simple and intuitive APIs. QNetworkAccessManager::get() and other request making functions returns pointer to QNetworkReply. Same pointer is returned in the parameter to QNetworkAccessManager::finished(). It is job of caller to delete QNetworkReply object but beware that you have to use QNetworkReply::deleteLater() if you want to delete the object inside the slot QNetworkAccessManager::finished(). QNetworkReply::rawHeaderList() is useful function which returns header list returned by server. RawRequestUi::processSngResponse() makes use of QNetworkReply::rawHeaderList(), QNetworkReply::rawHeader() to read HTTP reply headers.
Miscellaneous
Example code also makes use of QSettings to remember data entered in user input fields.
Example project
SISX File Media:HttpConsole template.sis
I've tried the example code on Nokia C5.00 (both firmware 032.010 and firmware 061.005) but the reply of a GET request to http://www.google.com.au/ using a 3G Network is always "Socket operation timed out".
What can be the matter?
I can browse Internet pages without problem using 3G Network and Nokia browser. I've compiled and deployed the example code for both Qt 4.6.3 and Qt 4.7.3, I get the same result above for both the cases.
polidorigi 13:34, 17 May 2011 (EEST)
Gurpal2000 - downloads incomplete files
on my nokia n8 this example seems to save an incomplete file. The md5sums of source and downloaded file are different!
-gurpal2000gurpal2000 00:07, 1 December 2012 (EET)
Hamishwillee - Downloads fine for me
I've also uploaded the SIS file separately. Suggest you try again.hamishwillee 07:21, 3 December 2012 (EET)