QNetworkAccessManager never emits finished() signal - c++

Question

I'm working on a module for a project where HTTP GET requests are used to retrieve some XML data, which is then converted to another format and send to a sub-system.
The code I have written so far is below:
CMakeLists.txt:
project(HttpDemo)
cmake_minimum_required(VERSION 2.8)
set(CMAKE_BUILD_TYPE Debug)
#find_package(Qt5Widgets)
find_package(Qt5Core)
find_package(Qt5Network)
set(CMAKE_AUTOMOC ON)
set(CMAKE_INCLUDE_CURRENT_DIR ON)
aux_source_directory(. SRC_LIST)
add_executable(${PROJECT_NAME} ${SRC_LIST})
qt5_use_modules(${PROJECT_NAME} Core Network) #Gui Widgets
main.cpp
#include <QtCore>
#include <QtNetwork>
class HttpHandler : public QObject
{
Q_OBJECT
public:
HttpHandler(QObject* parent=Q_NULLPTR) : QObject(parent)
{
QObject::connect(&nm, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));
qDebug() << QSslSocket::sslLibraryBuildVersionString();
}
private:
QNetworkAccessManager nm;
public slots:
void post(QString urlLink)
{
QUrl url(urlLink);
QNetworkRequest request(url);
QSslConfiguration sslConf;
sslConf.setProtocol(QSsl::SslV3);
request.setSslConfiguration(sslConf);
request.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencded");
QUrlQuery query;
query.addQueryItem("client_id", "1234");
query.addQueryItem("code", "abcd");
QUrl params;
params.setQuery(query);
nm.post(request, params.toEncoded());
}
void get(QString urlLink)
{
QUrl url(urlLink);
QNetworkRequest request(url);
request.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");
nm.get(request);
}
void replyFinished(QNetworkReply* reply)
{
QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);
if(statusCode.isValid())
{
// Print or catch the status code
QString status = statusCode.toString(); // or status_code.toInt();
qDebug() << status;
qDebug() << QString::fromStdString(reply->readAll().toStdString());
}
}
};
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
HttpHandler hh;
hh.get("SOME_URL");
return a.exec();
}
#include "main.moc"
With SOME_URL I have tried a lot of links all of which work without any issues in let's say the Http Requester addon for Firefox. I get:
"OpenSSL 1.0.1j 15 Oct 2014"
qt.network.ssl: QSslSocket: cannot resolve SSLv2_client_method
qt.network.ssl: QSslSocket: cannot resolve SSLv2_server_method
According to the authority called the Internet this shouldn't be a problem. One thing's for certain - my replyFinished(QNetworkReply*) slot doesn't get triggered although it is connected to the finished() signal of the QNetworkAccessManager. This means that whatever the reason the signal is not emitted. Changing the QSslConfiguration to a different QSsl::SslProtocol doesn't make a difference in the outcome.
UPDATE (as requested in the comments):
Following code uses readyRead() and dynamically allocated reply. The result - same as above.
#include <QtCore>
#include <QtNetwork>
class HttpHandler : public QObject
{
Q_OBJECT
public:
HttpHandler(QObject* parent=Q_NULLPTR) : QObject(parent)
{
qDebug() << QSslSocket::sslLibraryBuildVersionString();
this->manager = new QNetworkAccessManager(this);
this->reply = Q_NULLPTR;
}
private:
QNetworkAccessManager* manager;
QNetworkReply* reply;
signals:
void finished();
public slots:
void post(QString urlLink)
{
QUrl url(urlLink);
QNetworkRequest request(url);
QSslConfiguration sslConf;
sslConf.setProtocol(QSsl::SslV2);
request.setSslConfiguration(sslConf);
request.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");
QUrlQuery query;
query.addQueryItem("client_id", "1234");
query.addQueryItem("code", "abcd");
QUrl params;
params.setQuery(query);
manager->post(request, params.toEncoded());
}
void get(QString urlLink)
{
QUrl url(urlLink);
QNetworkRequest request(url);
request.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");
this->reply = manager->get(request);
QObject::connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));
}
void slotReadyRead()
{
qDebug() << "Hello"; // I never land here
}
void replyFinished(QNetworkReply* reply)
{
QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);
if(statusCode.isValid())
{
QString status = statusCode.toString(); // or status_code.toInt();
qDebug() << status;
qDebug() << QString::fromStdString(reply->readAll().toStdString());
}
emit finished();
}
};
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
HttpHandler *hh = new HttpHandler(&a);
QObject::connect(hh, SIGNAL(finished()), &a, SLOT(quit()));
hh->get("http://httpbin.org/ip"); // or any other httpbin.org endpoint
return a.exec();
}
#include "main.moc"
UPDATE 2:
I just found an example in the Qt documentation. Downloaded, compiled and ran the thing - same error but it works.

Answer 1

Issue resolved (see here). Basically the problem was the company's proxy. A colleague of mine gave it a shot and replaced the HTTP with HTTPS (even though the link is HTTP) and it worked all of a sudden. Then it struck us - the company's proxy caches HTTP (and does other things too), which leads to huge delays and if the timeout tolerance is small enough QNetworkAccessManager will return a socket timeout.
Using QNetworkProxyFactory::setUseSystemConfiguration(true) enables the proxy in a way that doesn't make your application dependent on a configuration in your code but rather the configuration of the system.