Qt QNetworkAccessManager & simple web service return - qt

Question

I have a simple web service with the following URL:
http://localhost:8080/WebSvc1/webresources/generic/data?ctype=Ping
This returns a simple XML data:
<CALL TYPE='Ping'><IP>10.0.0.10</IP></CALL>
I'm trying to write a Qt program to call this web service.
The code that makes the call is below:
QUrl qrl("http://localhost:8080/WebSvc1/webresources/generic/data?ctype=Ping");
manager = new QNetworkAccessManager(this);
connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));
printf ("Calling url: [%s]\n", qPrintable(url));
QNetworkReply *reply = 0;
reply = manager->get(QNetworkRequest(qrl));
qDebug() << reply->readAll();
I'm expecting/hoping the readAll will get the XML text data and print it (via qDebug).
Instead I see nothing and the program just hangs.
UPpdate, also have this:
void obj::replyFinished(QNetworkReply *reply)
{
qDebug() << reply->readAll();
}

Answer 1

I've included an example (forcing a synchronous request <-> reply exchange to easy the debugging process) that should work for you:
QUrl qrl("http://localhost:8080/WebSvc1/webresources/generic/data?ctype=Ping");
qDebug() << "Calling url: " << qrl.toString();
manager = new QNetworkAccessManager();
QNetworkReply* reply = manager->get(QNetworkRequest(qrl));
QEventLoop eventLoop;
connect(reply, SIGNAL(finished()), &eventLoop, SLOT(quit()));
eventLoop.exec();
if (reply->error() != QNetworkReply::NoError)
{
qDebug() << "Network error: " << reply->error();
}
else
{
qDebug() << reply->readAll();
}
Notice that the "emitter" of the finished signal is not the QNetworkAccessManager but the reply itself.

Answer 2

I think your error could be with your web service. I tried your code out (slightly modified) with httpbin.org, and was getting proper replies. Maybe take a look at your code with httpbin.org and then see if you can track down what's wrong with your service.
MainWindow.cpp
#include "MainWindow.hpp"
#include <QUrl>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QNetworkAccessManager>
#include <QDebug>
MainWindow::MainWindow(QWidget* parent)
: QMainWindow(parent), manager(this) {
load();
}
void MainWindow::load() {
const QUrl url(QStringLiteral("http://httpbin.org/xml"));
QNetworkReply* reply = manager.get(QNetworkRequest(url));
connect(reply, &QNetworkReply::finished, this, [this, reply]() {
replyFinished(reply);
});
qDebug() << reply->readAll(); // The reply won't be ready by now, so
// testing here isn't very helpful.
}
void MainWindow::replyFinished(QNetworkReply* reply) {
qDebug() << reply->readAll();
reply->deleteLater();
}
MainWindow.hpp
#ifndef MAINWINDOW_HPP
#define MAINWINDOW_HPP
#include <QMainWindow>
#include <QNetworkAccessManager>
#include <QNetworkReply>
class MainWindow : public QMainWindow {
Q_OBJECT
public:
explicit MainWindow(QWidget* parent = nullptr);
public slots:
void load();
void replyFinished(QNetworkReply* reply);
private:
QNetworkAccessManager manager;
};
#endif // MAINWINDOW_HPP
main.cpp
#include "MainWindow.hpp"
#include <QApplication>
int main(int argc, char* argv[]) {
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
network.pro
QT += core gui widgets network
TARGET = network
TEMPLATE = app
DEFINES += QT_DEPRECATED_WARNINGS
CONFIG += c++11
SOURCES += \
main.cpp \
MainWindow.cpp
HEADERS += MainWindow.hpp