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/****************************************************************************
**
** Copyright (C) 2019 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** 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.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
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****************************************************************************/
/*!
\example simplecoapclient
\title Simple CoAP Client Example
\ingroup qtcoap-examples
\brief Creating an application that communicates with a CoAP server.
\image simplecoapclient.png
\e {Simple CoAP Client} demonstrates how to create a minimalistic CoAP client
application to send and receive CoAP messages.
\section1 Setting Up a CoAP Server
To use the application, you need to specify a CoAP server. You have the following
options:
\list
\li Use the CoAP test server located at \c {coap://coap.me}.
\li Create a CoAP server using \l {https://github.com/obgm/libcoap} {libcoap},
\l {https://github.com/keith-cullen/FreeCoAP} {FreeCoAP} or any other CoAP
server implementation.
\li Use the \l {https://github.com/eclipse/californium/} {Californium} plugtest
server, which supports most of the CoAP features. You can build it manually or
use a ready Docker image, which builds and starts the plugtest server. The steps
for using the docker-based server are described below.
\endlist
\section2 Using the Docker-based Test Server
The following command pulls the docker container for the CoAP server from the Docker
Hub and starts it:
\badcode
docker run --name coap-test-server -d --rm -p 5683:5683/udp -p 5684:5684/udp sokurazy/coap-secure-test-server:californium.1.1.0
\endcode
To find out the IP address of the docker container, first retrieve the container ID
by running \c {docker ps}, which will output something like:
\badcode
$ docker ps
CONTAINER ID IMAGE
5e46502df88f sonakur/coap-secure-test-server:californium.1.1.0
\endcode
Then you can obtain the IP address with the following command:
\badcode
docker inspect <container_id> | grep IPAddress
\endcode
For example:
\badcode
$ docker inspect 5e46502df88f | grep IPAddress
...
"IPAddress": "172.17.0.2",
...
\endcode
The CoAP test server will be reachable by the retrieved IP address on ports
\e 5683 (non-secure) and \e 5684 (secure).
\section1 Creating a Client
The first step is to create a CoAP client using the QCoapClient class. Then
we need to connect its signals, to get notified when a CoAP reply is received
or a request has failed:
\quotefromfile simplecoapclient/mainwindow.cpp
\skipto MainWindow::MainWindow
\printuntil onError
\dots
\section1 Sending Requests
We use the QCoapRequest class to create CoAP requests. This class provides methods
for constructing CoAP frames.
\skipto on_runButton_clicked
\printuntil addOption
\dots
In this example, we set the URL, as well as the message type and add options
to the request. It is also possible to set the payload, message ID, token,
and so on, but we are using the default values here. Note that by default,
the message ID and token are generated randomly.
Based on the selected request method, we send a \c GET, \c PUT, \c POST or
\c DELETE request to the server:
\skipto switch
\dots
\printuntil }
\dots
For \c PUT and \c POST requests we also add \c m_currentData as a payload for
the request.
For browsing the contents of the server and discovering the resources available on
it, a \e discovery request is used:
\skipto on_discoverButton_clicked
\printuntil {
\dots
\skipto discoverReply
\printuntil onDiscovered
\dots
\note Instead of QCoapReply class, we use the QCoapResourceDiscoveryReply to keep
the reply for a discovery request. It has the QCoapResourceDiscoveryReply::discovered
signal, which returns the list of QCoapResources that has been discovered.
If there are \e observable resources on the server (meaning that they have the
resource type \c obs), we can subscribe to updates on that resource by running
an \e observe request:
\skipto on_observeButton_clicked
\printuntil {
\dots
\skipto observeReply
\printline observeReply
\dots
\skipto onNotified
\printline onNotified
\dots
The client can unsubscribe from the resource observation by handling the
\c clicked() signal of the \c cancelObserveButton:
\skipto clicked
\dots
\printuntil })
The responses coming from the server are displayed in the UI:
\quotefromfile simplecoapclient/mainwindow.cpp
\skipto MainWindow::addMessage
\printto on_runButton_clicked
*/
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