Quick Secure CoAP Client Example

 // Copyright (C) 2019 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

 #include "qmlcoapsecureclient.h"

 #include <QCoapReply>
 #include <QFile>
 #include <QLoggingCategory>
 #include <QMetaEnum>
 #include <QUrl>

 Q_LOGGING_CATEGORY(lcCoapClient, "qt.coap.client")

 QmlCoapSecureClient::QmlCoapSecureClient(QObject *parent)
     : QObject(parent)
     , m_coapClient(nullptr)
     , m_securityMode(QtCoap::SecurityMode::NoSecurity)
 {
 }

 QmlCoapSecureClient::~QmlCoapSecureClient()
 {
     if (m_coapClient) {
         delete m_coapClient;
         m_coapClient = nullptr;
     }
 }

 static QString errorMessage(QtCoap::Error errorCode)
 {
     const auto error = QMetaEnum::fromType<QtCoap::Error>().valueToKey(static_cast<int>(errorCode));
     return QString("Request failed with error: %1\n").arg(error);
 }

 void QmlCoapSecureClient::setSecurityMode(QtCoap::SecurityMode mode)
 {
     // Create a new client, if the security mode has changed
     if (m_coapClient && mode != m_securityMode) {
         delete m_coapClient;
         m_coapClient = nullptr;
     }

     if (!m_coapClient) {
         m_coapClient = new QCoapClient(mode);
         m_securityMode = mode;

         connect(m_coapClient, &QCoapClient::finished, this,
                 [this](QCoapReply *reply) {
                     if (!reply)
                         emit finished("Something went wrong, received a null reply");
                     else if (reply->errorReceived() != QtCoap::Error::Ok)
                         emit finished(errorMessage(reply->errorReceived()));
                     else
                         emit finished(reply->message().payload());
                 });

         connect(m_coapClient, &QCoapClient::error, this,
                 [this](QCoapReply *, QtCoap::Error errorCode) {
                     emit finished(errorMessage(errorCode));
                 });
     }
 }

 void QmlCoapSecureClient::sendGetRequest(const QString &host, const QString &path, int port)
 {
     if (!m_coapClient)
         return;

     m_coapClient->setSecurityConfiguration(m_configuration);

     QUrl url;
     url.setHost(host);
     url.setPath(path);
     url.setPort(port);
     m_coapClient->get(url);
 }

 void
 QmlCoapSecureClient::setSecurityConfiguration(const QString &preSharedKey, const QString &identity)
 {
     QCoapSecurityConfiguration configuration;
     configuration.setPreSharedKey(preSharedKey.toUtf8());
     configuration.setPreSharedKeyIdentity(identity.toUtf8());
     m_configuration = configuration;
 }

 void QmlCoapSecureClient::setSecurityConfiguration(const QString &localCertificatePath,
                                                    const QString &caCertificatePath,
                                                    const QString &privateKeyPath)
 {
     QCoapSecurityConfiguration configuration;

     const auto localCerts =
             QSslCertificate::fromPath(QUrl(localCertificatePath).toLocalFile(), QSsl::Pem,
                                       QSslCertificate::PatternSyntax::FixedString);
     if (localCerts.isEmpty())
         qCWarning(lcCoapClient, "The specified local certificate file is not valid.");
     else
         configuration.setLocalCertificateChain(localCerts.toVector());

     const auto caCerts = QSslCertificate::fromPath(QUrl(caCertificatePath).toLocalFile(), QSsl::Pem,
                                                    QSslCertificate::PatternSyntax::FixedString);
     if (caCerts.isEmpty())
         qCWarning(lcCoapClient, "The specified CA certificate file is not valid.");
     else
         configuration.setCaCertificates(caCerts.toVector());

     QFile privateKey(QUrl(privateKeyPath).toLocalFile());
     if (privateKey.open(QIODevice::ReadOnly)) {
         QCoapPrivateKey key(privateKey.readAll(), QSsl::Ec);
         configuration.setPrivateKey(key);
     } else {
         qCWarning(lcCoapClient) << "Unable to read the specified private key file"
                                 << privateKeyPath;
     }
     m_configuration = configuration;
 }

 void QmlCoapSecureClient::disconnect()
 {
     if (m_coapClient)
         m_coapClient->disconnect();
 }