/// <summary>
/// Subscribe for message topics
/// </summary>
/// <param name="topics">List of topics to subscribe</param>
/// <param name="qosLevels">QOS levels related to topics</param>
/// <returns>Granted QoS Levels in SUBACK message from broker</returns>
public byte[] Subscribe(string[] topics, byte[] qosLevels)
{
int attempts = 0;
bool acknowledged = false;
MqttMsgSubscribe subscribe =
new MqttMsgSubscribe(topics, qosLevels);
MqttMsgSuback suback = null;
do
{
try
{
// try subscribe
suback = (MqttMsgSuback)this.SendReceive(subscribe.GetBytes());
acknowledged = true;
}
catch (MqttTimeoutException)
{
// no SUBACK message received in time, retry with duplicate flag
attempts++;
subscribe.DupFlag = true;
// delay before retry
if (attempts < MQTT_ATTEMPTS_RETRY)
{
Thread.Sleep(MQTT_DELAY_RETRY);
}
}
} while ((attempts < MQTT_ATTEMPTS_RETRY) && !acknowledged);
// return granted QoS Levels or null
return(acknowledged ? suback.GrantedQoSLevels : null);
}
