Add CoAP client example

Simple Qt Widgets based example demonstrating how to use CoAP API.
Covers:
 - Sending GET/POST/PUT/DELETE requests
 - Observing resources
 - Resource discovery

Change-Id: I2abb3fd670ff86958e73331413d1f0d0e8ce4a5d
Reviewed-by: Karsten Heimrich <karsten.heimrich@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

9 files changed, 1162 insertions, 0 deletions

diff --git a/examples/examples.pro b/examples/examples.pro
index 0490212..619c9e5 100644
--- a/examples/examples.pro
+++ b/examples/examples.pro
@@ -2,4 +2,5 @@ TEMPLATE = subdirs
 CONFIG += no_docs_target
 
 SUBDIRS += \
+    simplecoapclient \
     testapp
diff --git a/examples/simplecoapclient/main.cpp b/examples/simplecoapclient/main.cpp
new file mode 100644
index 0000000..2968a11
--- /dev/null
+++ b/examples/simplecoapclient/main.cpp
@@ -0,0 +1,62 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtCoap module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "mainwindow.h"
+
+#include <QApplication>
+
+int main(int argc, char *argv[])
+{
+    QApplication a(argc, argv);
+    MainWindow w;
+    w.show();
+
+    return a.exec();
+}
diff --git a/examples/simplecoapclient/mainwindow.cpp b/examples/simplecoapclient/mainwindow.cpp
new file mode 100644
index 0000000..f133650
--- /dev/null
+++ b/examples/simplecoapclient/mainwindow.cpp
@@ -0,0 +1,248 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtCoap module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "mainwindow.h"
+#include "optiondialog.h"
+#include "ui_mainwindow.h"
+
+#include <QCoapDiscoveryReply>
+#include <QCoapReply>
+#include <QDateTime>
+#include <QFileDialog>
+#include <QMessageBox>
+#include <QMetaEnum>
+#include <QNetworkInterface>
+
+MainWindow::MainWindow(QWidget *parent) :
+    QMainWindow(parent),
+    ui(new Ui::MainWindow),
+    m_client(new QCoapClient(QtCoap::NoSec, this))
+{
+    ui->setupUi(this);
+
+    ui->methodComboBox->addItem("Get", QtCoap::Method::Get);
+    ui->methodComboBox->addItem("Put", QtCoap::Method::Put);
+    ui->methodComboBox->addItem("Post", QtCoap::Method::Post);
+    ui->methodComboBox->addItem("Delete", QtCoap::Method::Delete);
+
+    fillHostSelector();
+    ui->hostComboBox->setFocus();
+
+    connect(m_client, &QCoapClient::finished, this, &MainWindow::onFinished);
+    connect(m_client, &QCoapClient::error, this, &MainWindow::onError);
+}
+
+MainWindow::~MainWindow()
+{
+    delete ui;
+}
+
+void MainWindow::fillHostSelector()
+{
+    const auto networkInterfaces = QNetworkInterface::allInterfaces();
+    for (const auto &interface : networkInterfaces)
+        for (const auto &address : interface.addressEntries())
+            ui->hostComboBox->addItem(address.ip().toString());
+}
+
+void MainWindow::addMessage(const QString &message, bool isError)
+{
+    const QString content = "--------------- "
+            + QDateTime::currentDateTime().toString()
+            + " ---------------\n"
+            + message + "\n\n";
+    ui->textEdit->setTextColor(isError ? Qt::red : Qt::black);
+    ui->textEdit->insertPlainText(content);
+    ui->textEdit->ensureCursorVisible();
+}
+
+void MainWindow::onFinished(QCoapReply *reply)
+{
+    if (reply->errorReceived() == QtCoap::NoError)
+        addMessage(reply->message().payload());
+}
+
+static QString errorMessage(QtCoap::Error errorCode)
+{
+    const auto error = QMetaEnum::fromType<QtCoap::Error>().valueToKey(errorCode);
+    return QString("Request failed with error: %1\n").arg(error);
+}
+
+void MainWindow::onError(QCoapReply *reply, QtCoap::Error error)
+{
+    const auto errorCode = reply ? reply->errorReceived() : error;
+    addMessage(errorMessage(errorCode), true);
+}
+
+void MainWindow::onDiscovered(QCoapDiscoveryReply *reply, QVector<QCoapResource> resources)
+{
+    if (reply->errorReceived() != QtCoap::NoError)
+        return;
+
+    QString message;
+    for (const auto &resource : resources) {
+        ui->resourceComboBox->addItem(resource.path());
+        message += "Discovered resource: \"" + resource.title() + "\" on path "
+                + resource.path() + "\n";
+    }
+    addMessage(message);
+}
+
+void MainWindow::onNotified(QCoapReply *reply, const QCoapMessage &message)
+{
+    if (reply->errorReceived() == QtCoap::NoError)
+        addMessage("Received observe notification with payload: " + message.payload());
+}
+
+void MainWindow::on_runButton_clicked()
+{
+    const auto msgType = ui->msgTypeCheckBox->isChecked() ? QCoapMessage::Confirmable
+                                                          : QCoapMessage::NonConfirmable;
+    QUrl url;
+    url.setHost(ui->hostComboBox->currentText());
+    url.setPort(ui->portSpinBox->value());
+    url.setPath(ui->resourceComboBox->currentText());
+
+    QCoapRequest request(url, msgType);
+    for (const auto &option : m_options)
+        request.addOption(option);
+    m_options.clear();
+
+    const auto method = ui->methodComboBox->currentData(Qt::UserRole).value<QtCoap::Method>();
+    switch (method) {
+    case QtCoap::Get:
+        m_client->get(request);
+        break;
+    case QtCoap::Put:
+        m_client->put(request, m_currentData);
+        break;
+    case QtCoap::Post:
+        m_client->post(request, m_currentData);
+        break;
+    case QtCoap::Delete:
+        m_client->deleteResource(request);
+        break;
+    default:
+        break;
+    }
+    m_currentData.clear();
+}
+
+void MainWindow::on_discoverButton_clicked()
+{
+    QUrl url;
+    url.setHost(ui->hostComboBox->currentText());
+    url.setPort(ui->portSpinBox->value());
+
+    QCoapDiscoveryReply *discoverReply = m_client->discover(url, ui->discoveryPathEdit->text());
+    if (discoverReply)
+        connect(discoverReply, &QCoapDiscoveryReply::discovered, this, &MainWindow::onDiscovered);
+    else
+        QMessageBox::critical(this, "Error", "Something went wrong, discovery request failed.");
+}
+
+void MainWindow::on_observeButton_clicked()
+{
+    QUrl url;
+    url.setHost(ui->hostComboBox->currentText());
+    url.setPort(ui->portSpinBox->value());
+    url.setPath(ui->resourceComboBox->currentText());
+
+    QCoapReply *observeReply = m_client->observe(url);
+    if (!observeReply) {
+        QMessageBox::critical(this, "Error", "Something went wrong, observe request failed.");
+        return;
+    }
+
+    connect(observeReply, &QCoapReply::notified, this, &MainWindow::onNotified);
+
+    ui->cancelObserveButton->setEnabled(true);
+    connect(ui->cancelObserveButton, &QPushButton::clicked, this, [&]() {
+        m_client->cancelObserve(url);
+        ui->cancelObserveButton->setEnabled(false);
+    });
+}
+
+void MainWindow::on_addOptionsButton_clicked()
+{
+    OptionDialog dialog;
+    if (dialog.exec() == QDialog::Accepted)
+        m_options = dialog.options();
+}
+
+void MainWindow::on_contentButton_clicked()
+{
+    QFileDialog dialog(this);
+    dialog.setFileMode(QFileDialog::AnyFile);
+    if (!dialog.exec())
+        return;
+
+    const auto fileName = dialog.selectedFiles().back();
+    QFile file(fileName);
+    if (!file.open(QIODevice::ReadOnly)) {
+        QMessageBox::critical(this, "Error", QString("Failed to read from file %1").arg(fileName));
+        return;
+    }
+
+    m_currentData = file.readAll();
+}
+
+void MainWindow::on_resourceComboBox_editTextChanged(const QString &text)
+{
+    ui->observeButton->setEnabled(!text.isEmpty());
+}
+
+void MainWindow::on_methodComboBox_currentIndexChanged(int index)
+{
+    Q_UNUSED(index);
+
+    const auto method = ui->methodComboBox->currentData(Qt::UserRole).value<QtCoap::Method>();
+    ui->contentButton->setEnabled(method == QtCoap::Put || method == QtCoap::Post);
+}
diff --git a/examples/simplecoapclient/mainwindow.h b/examples/simplecoapclient/mainwindow.h
new file mode 100644
index 0000000..a561c0e
--- /dev/null
+++ b/examples/simplecoapclient/mainwindow.h
@@ -0,0 +1,99 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtCoap module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef MAINWINDOW_H
+#define MAINWINDOW_H
+
+#include <QCoapClient>
+#include <QCoapOption>
+#include <QCoapResource>
+#include <QMainWindow>
+
+QT_BEGIN_NAMESPACE
+namespace Ui {
+class MainWindow;
+}
+class QCoapMessage;
+QT_END_NAMESPACE
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+
+public:
+    explicit MainWindow(QWidget *parent = nullptr);
+    ~MainWindow();
+
+private:
+    void fillHostSelector();
+    void addMessage(const QString &message, bool isError = false);
+
+private slots:
+    void onFinished(QCoapReply *reply);
+    void onError(QCoapReply *reply, QtCoap::Error error);
+    void onDiscovered(QCoapDiscoveryReply *reply, QVector<QCoapResource> resources);
+    void onNotified(QCoapReply *reply, const QCoapMessage &message);
+
+    void on_runButton_clicked();
+    void on_discoverButton_clicked();
+    void on_observeButton_clicked();
+    void on_addOptionsButton_clicked();
+    void on_contentButton_clicked();
+    void on_resourceComboBox_editTextChanged(const QString &text);
+    void on_methodComboBox_currentIndexChanged(int index);
+
+private:
+    Ui::MainWindow *ui;
+    QCoapClient *m_client;
+    QVector<QCoapOption> m_options;
+    QByteArray m_currentData;
+};
+
+#endif // MAINWINDOW_H
diff --git a/examples/simplecoapclient/mainwindow.ui b/examples/simplecoapclient/mainwindow.ui
new file mode 100644
index 0000000..f6cff95
--- /dev/null
+++ b/examples/simplecoapclient/mainwindow.ui
@@ -0,0 +1,360 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>MainWindow</class>
+ <widget class="QMainWindow" name="MainWindow">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>731</width>
+    <height>530</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>CoAP Client</string>
+  </property>
+  <widget class="QWidget" name="centralWidget">
+   <layout class="QGridLayout" name="gridLayout_3">
+    <item row="0" column="0">
+     <layout class="QGridLayout" name="gridLayout">
+      <item row="0" column="0">
+       <widget class="QLabel" name="label">
+        <property name="text">
+         <string>Host</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="4" column="0">
+       <widget class="QLabel" name="label_4">
+        <property name="text">
+         <string>Request Method</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="3" column="1">
+       <layout class="QHBoxLayout" name="horizontalLayout_2">
+        <item>
+         <widget class="QComboBox" name="resourceComboBox">
+          <property name="sizePolicy">
+           <sizepolicy hsizetype="MinimumExpanding" vsizetype="Fixed">
+            <horstretch>0</horstretch>
+            <verstretch>0</verstretch>
+           </sizepolicy>
+          </property>
+          <property name="editable">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QPushButton" name="observeButton">
+          <property name="enabled">
+           <bool>false</bool>
+          </property>
+          <property name="text">
+           <string>Observe</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <spacer name="horizontalSpacer_3">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>40</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+       </layout>
+      </item>
+      <item row="0" column="1">
+       <layout class="QHBoxLayout" name="horizontalLayout_5">
+        <item>
+         <widget class="QComboBox" name="hostComboBox">
+          <property name="sizePolicy">
+           <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
+            <horstretch>0</horstretch>
+            <verstretch>0</verstretch>
+           </sizepolicy>
+          </property>
+          <property name="minimumSize">
+           <size>
+            <width>250</width>
+            <height>0</height>
+           </size>
+          </property>
+          <property name="editable">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <spacer name="horizontalSpacer">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeType">
+           <enum>QSizePolicy::Expanding</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>40</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+       </layout>
+      </item>
+      <item row="4" column="1">
+       <layout class="QHBoxLayout" name="horizontalLayout_3">
+        <item>
+         <widget class="QComboBox" name="methodComboBox">
+          <property name="sizePolicy">
+           <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
+            <horstretch>0</horstretch>
+            <verstretch>0</verstretch>
+           </sizepolicy>
+          </property>
+          <property name="minimumSize">
+           <size>
+            <width>150</width>
+            <height>0</height>
+           </size>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QCheckBox" name="msgTypeCheckBox">
+          <property name="text">
+           <string>Confirmable</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QPushButton" name="addOptionsButton">
+          <property name="text">
+           <string>Add Options</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QPushButton" name="contentButton">
+          <property name="enabled">
+           <bool>false</bool>
+          </property>
+          <property name="text">
+           <string>Add Content</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <spacer name="horizontalSpacer_4">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>40</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+       </layout>
+      </item>
+      <item row="2" column="0">
+       <widget class="QLabel" name="label_8">
+        <property name="text">
+         <string>Disscovery Path:</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="6" column="0" colspan="2">
+       <widget class="QGroupBox" name="groupBox">
+        <property name="title">
+         <string>Output</string>
+        </property>
+        <layout class="QGridLayout" name="gridLayout_2">
+         <item row="0" column="0">
+          <widget class="QTextEdit" name="textEdit">
+           <property name="readOnly">
+            <bool>true</bool>
+           </property>
+          </widget>
+         </item>
+        </layout>
+       </widget>
+      </item>
+      <item row="1" column="0">
+       <widget class="QLabel" name="label_2">
+        <property name="text">
+         <string>Port</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="5" column="1">
+       <layout class="QHBoxLayout" name="horizontalLayout_12">
+        <item>
+         <widget class="QPushButton" name="runButton">
+          <property name="text">
+           <string>Run</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QPushButton" name="cancelObserveButton">
+          <property name="enabled">
+           <bool>false</bool>
+          </property>
+          <property name="text">
+           <string>Cancel Observe</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <spacer name="horizontalSpacer_6">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>40</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+       </layout>
+      </item>
+      <item row="3" column="0">
+       <widget class="QLabel" name="label_3">
+        <property name="text">
+         <string>Resource</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="2" column="1">
+       <layout class="QHBoxLayout" name="horizontalLayout_13">
+        <item>
+         <widget class="QLineEdit" name="discoveryPathEdit">
+          <property name="text">
+           <string>/.well-known/core</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QPushButton" name="discoverButton">
+          <property name="text">
+           <string>Discover</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <spacer name="horizontalSpacer_7">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>40</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+       </layout>
+      </item>
+      <item row="1" column="1">
+       <layout class="QHBoxLayout" name="horizontalLayout_6">
+        <item>
+         <widget class="QSpinBox" name="portSpinBox">
+          <property name="sizePolicy">
+           <sizepolicy hsizetype="Minimum" vsizetype="Fixed">
+            <horstretch>0</horstretch>
+            <verstretch>0</verstretch>
+           </sizepolicy>
+          </property>
+          <property name="minimumSize">
+           <size>
+            <width>100</width>
+            <height>0</height>
+           </size>
+          </property>
+          <property name="maximum">
+           <number>65535</number>
+          </property>
+          <property name="value">
+           <number>5683</number>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <spacer name="horizontalSpacer_2">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>40</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+       </layout>
+      </item>
+      <item row="5" column="0">
+       <widget class="QLabel" name="label_7">
+        <property name="text">
+         <string/>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </item>
+   </layout>
+  </widget>
+  <widget class="QMenuBar" name="menuBar">
+   <property name="geometry">
+    <rect>
+     <x>0</x>
+     <y>0</y>
+     <width>731</width>
+     <height>22</height>
+    </rect>
+   </property>
+  </widget>
+  <widget class="QToolBar" name="mainToolBar">
+   <attribute name="toolBarArea">
+    <enum>TopToolBarArea</enum>
+   </attribute>
+   <attribute name="toolBarBreak">
+    <bool>false</bool>
+   </attribute>
+  </widget>
+  <widget class="QStatusBar" name="statusBar"/>
+ </widget>
+ <layoutdefault spacing="6" margin="11"/>
+ <resources/>
+ <connections/>
+</ui>
diff --git a/examples/simplecoapclient/optiondialog.cpp b/examples/simplecoapclient/optiondialog.cpp
new file mode 100644
index 0000000..5125541
--- /dev/null
+++ b/examples/simplecoapclient/optiondialog.cpp
@@ -0,0 +1,121 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtCoap module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "optiondialog.h"
+#include "ui_optiondialog.h"
+
+OptionDialog::OptionDialog(QWidget *parent) :
+    QDialog(parent),
+    ui(new Ui::OptionDialog)
+{
+    ui->setupUi(this);
+
+    fillOptions();
+
+    auto header = ui->tableWidget->horizontalHeader();
+    header->setSectionResizeMode(QHeaderView::Stretch);
+}
+
+OptionDialog::~OptionDialog()
+{
+    delete ui;
+}
+
+QVector<QCoapOption> OptionDialog::options() const
+{
+    return m_options;
+}
+
+void OptionDialog::on_addButton_clicked()
+{
+    const auto option =
+            ui->optionComboBox->currentData(Qt::UserRole).value<QCoapOption::OptionName>();
+    m_options.push_back(QCoapOption(option, ui->optionValueEdit->text()));
+
+    const auto rowCount = ui->tableWidget->rowCount();
+    ui->tableWidget->insertRow(rowCount);
+
+    QTableWidgetItem *optionItem = new QTableWidgetItem(ui->optionComboBox->currentText());
+    optionItem->setFlags(optionItem->flags() ^ Qt::ItemIsEditable);
+    ui->tableWidget->setItem(rowCount, 0, optionItem);
+
+    QTableWidgetItem *valueItem = new QTableWidgetItem(ui->optionValueEdit->text());
+    valueItem->setFlags(valueItem->flags() ^ Qt::ItemIsEditable);
+    ui->tableWidget->setItem(rowCount, 1, valueItem);
+}
+
+void OptionDialog::on_clearButton_clicked()
+{
+    m_options.clear();
+    ui->tableWidget->setRowCount(0);
+}
+
+void OptionDialog::fillOptions()
+{
+    ui->tableWidget->setHorizontalHeaderLabels({"Name", "Value"});
+    ui->optionComboBox->addItem("None", QCoapOption::Invalid);
+    ui->optionComboBox->addItem("Block1", QCoapOption::Block1);
+    ui->optionComboBox->addItem("Block2", QCoapOption::Block2);
+    ui->optionComboBox->addItem("Content-Format", QCoapOption::ContentFormat);
+    ui->optionComboBox->addItem("If-Match", QCoapOption::IfMatch);
+    ui->optionComboBox->addItem("If-None-Match", QCoapOption::IfNoneMatch);
+    ui->optionComboBox->addItem("Location-Path", QCoapOption::LocationPath);
+    ui->optionComboBox->addItem("Location-Query", QCoapOption::LocationQuery);
+    ui->optionComboBox->addItem("Max-Age", QCoapOption::MaxAge);
+    ui->optionComboBox->addItem("Observe", QCoapOption::Observe);
+    ui->optionComboBox->addItem("Proxy-Scheme", QCoapOption::ProxyScheme);
+    ui->optionComboBox->addItem("Proxy-Uri", QCoapOption::ProxyUri);
+    ui->optionComboBox->addItem("Size1", QCoapOption::Size1);
+    ui->optionComboBox->addItem("Size2", QCoapOption::Size2);
+    ui->optionComboBox->addItem("Uri-Host", QCoapOption::UriHost);
+    ui->optionComboBox->addItem("Uri-Path", QCoapOption::UriPath);
+    ui->optionComboBox->addItem("Uri-Port", QCoapOption::UriPort);
+    ui->optionComboBox->addItem("Uri-Query", QCoapOption::UriQuery);
+}
diff --git a/examples/simplecoapclient/optiondialog.h b/examples/simplecoapclient/optiondialog.h
new file mode 100644
index 0000000..ecd0b34
--- /dev/null
+++ b/examples/simplecoapclient/optiondialog.h
@@ -0,0 +1,84 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the QtCoap module.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef OPTIONDIALOG_H
+#define OPTIONDIALOG_H
+
+#include <QCoapOption>
+#include <QDialog>
+
+QT_BEGIN_NAMESPACE
+namespace Ui {
+class OptionDialog;
+}
+QT_END_NAMESPACE
+
+class OptionDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    explicit OptionDialog(QWidget *parent = nullptr);
+    ~OptionDialog();
+
+    QVector<QCoapOption> options() const;
+
+private slots:
+    void on_addButton_clicked();
+    void on_clearButton_clicked();
+
+private:
+    void fillOptions();
+
+    Ui::OptionDialog *ui;
+    QVector<QCoapOption> m_options;
+};
+
+#endif // OPTIONDIALOG_H
diff --git a/examples/simplecoapclient/optiondialog.ui b/examples/simplecoapclient/optiondialog.ui
new file mode 100644
index 0000000..7313b32
--- /dev/null
+++ b/examples/simplecoapclient/optiondialog.ui
@@ -0,0 +1,154 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>OptionDialog</class>
+ <widget class="QDialog" name="OptionDialog">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>414</width>
+    <height>313</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Add Options</string>
+  </property>
+  <layout class="QHBoxLayout" name="horizontalLayout_3">
+   <item>
+    <layout class="QHBoxLayout" name="horizontalLayout_2">
+     <item>
+      <layout class="QVBoxLayout" name="verticalLayout_2">
+       <item>
+        <layout class="QHBoxLayout" name="horizontalLayout">
+         <item>
+          <widget class="QLabel" name="label">
+           <property name="text">
+            <string>Option</string>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <widget class="QComboBox" name="optionComboBox">
+           <property name="sizePolicy">
+            <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
+             <horstretch>0</horstretch>
+             <verstretch>0</verstretch>
+            </sizepolicy>
+           </property>
+           <property name="minimumSize">
+            <size>
+             <width>120</width>
+             <height>0</height>
+            </size>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <widget class="QLineEdit" name="optionValueEdit"/>
+         </item>
+        </layout>
+       </item>
+       <item>
+        <widget class="QTableWidget" name="tableWidget">
+         <property name="columnCount">
+          <number>2</number>
+         </property>
+         <column/>
+         <column/>
+        </widget>
+       </item>
+       <item>
+        <widget class="QDialogButtonBox" name="buttonBox">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+         <property name="standardButtons">
+          <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
+         </property>
+        </widget>
+       </item>
+      </layout>
+     </item>
+     <item>
+      <layout class="QVBoxLayout" name="verticalLayout">
+       <item>
+        <widget class="QPushButton" name="addButton">
+         <property name="sizePolicy">
+          <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
+           <horstretch>0</horstretch>
+           <verstretch>0</verstretch>
+          </sizepolicy>
+         </property>
+         <property name="minimumSize">
+          <size>
+           <width>100</width>
+           <height>0</height>
+          </size>
+         </property>
+         <property name="text">
+          <string>Add</string>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QPushButton" name="clearButton">
+         <property name="text">
+          <string>Clear</string>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <spacer name="verticalSpacer">
+         <property name="orientation">
+          <enum>Qt::Vertical</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>20</width>
+           <height>40</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
+      </layout>
+     </item>
+    </layout>
+   </item>
+  </layout>
+ </widget>
+ <resources/>
+ <connections>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>accepted()</signal>
+   <receiver>OptionDialog</receiver>
+   <slot>accept()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>152</x>
+     <y>289</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>206</x>
+     <y>156</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>rejected()</signal>
+   <receiver>OptionDialog</receiver>
+   <slot>reject()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>152</x>
+     <y>289</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>206</x>
+     <y>156</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
+</ui>
diff --git a/examples/simplecoapclient/simplecoapclient.pro b/examples/simplecoapclient/simplecoapclient.pro
new file mode 100644
index 0000000..16fa118
--- /dev/null
+++ b/examples/simplecoapclient/simplecoapclient.pro
@@ -0,0 +1,33 @@
+QT       += core gui network coap widgets
+
+TARGET = simplecoapclient
+TEMPLATE = app
+
+# The following define makes your compiler emit warnings if you use
+# any feature of Qt which has been marked as deprecated (the exact warnings
+# depend on your compiler). Please consult the documentation of the
+# deprecated API in order to know how to port your code away from it.
+DEFINES += QT_DEPRECATED_WARNINGS
+
+# You can also make your code fail to compile if you use deprecated APIs.
+# In order to do so, uncomment the following line.
+# You can also select to disable deprecated APIs only up to a certain version of Qt.
+#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
+
+CONFIG += c++11
+
+SOURCES += \
+        main.cpp \
+        mainwindow.cpp \
+        optiondialog.cpp
+
+HEADERS += \
+        mainwindow.h \
+        optiondialog.h
+
+FORMS += \
+        mainwindow.ui \
+        optiondialog.ui
+
+target.path = $$[QT_INSTALL_EXAMPLES]/simplecoapclient
+INSTALLS += target