Method runTestConnection

app/src/MQTT/Publisher.cpp:670–729

* @brief Runs an out-of-band connection probe using a throwaway QMqttClient. */

 * @brief Runs an out-of-band connection probe using a throwaway QMqttClient.
 */
void MQTT::PublisherWorker::runTestConnection()
{
  if (m_cfg.hostname.isEmpty() || m_cfg.port == 0) {
    Q_EMIT testConnectionFinished(
      false, tr("Configure broker hostname and port before testing the connection."));
    return;
  }

  auto* tester = new QMqttClient(this);
  tester->setHostname(m_cfg.hostname);
  tester->setPort(m_cfg.port);
  tester->setClientId(m_cfg.clientId + QStringLiteral("-probe"));
  tester->setUsername(m_cfg.username);
  tester->setPassword(m_cfg.password);
  tester->setCleanSession(true);
  tester->setKeepAlive(5);
  tester->setProtocolVersion(m_cfg.mqttVersion);

  auto* timeout = new QTimer(tester);
  timeout->setSingleShot(true);
  timeout->setInterval(5000);

  auto done   = std::make_shared<bool>(false);
  auto report = [this, tester, done](bool ok, const QString& detail) {
    if (*done)
      return;

    *done = true;
    if (tester->state() != QMqttClient::Disconnected)
      tester->disconnectFromHost();

    Q_EMIT testConnectionFinished(ok, detail);

    tester->deleteLater();
  };

  connect(
    tester, &QMqttClient::stateChanged, this, [tester, report](QMqttClient::ClientState state) {
      if (state == QMqttClient::Connected)
        report(true,
               tr("Successfully connected to %1:%2.").arg(tester->hostname()).arg(tester->port()));
    });

  connect(tester, &QMqttClient::errorChanged, this, [report](QMqttClient::ClientError error) {
    if (error == QMqttClient::NoError)
      return;

    report(false, describeMqttError(error));
  });

  connect(timeout, &QTimer::timeout, this, [report] {
    report(false, tr("Timed out after 5 seconds without reaching the broker."));
  });

  timeout->start();
  if (m_cfg.sslEnabled)
    tester->connectToHostEncrypted(m_sslConfiguration);
  else