How to set connect_flags? about mqtt-c HOT 1 CLOSED

Yeah, no problem. The 8th argument to mqtt_connect are the connect flags. These flags are enumerated in enum MQTTConnectFlags on line 587 of mqtt.h.

For example, if you want to set "clean session" you would pass MQTT_CONNECT_CLEAN_SESSION as the 8th argument to mqtt_connect.

If you want to set multiple flags, for example, "clean session" and a will with QoS level 2, you would pass MQTT_CONNECT_CLEAN_SESSION | MQTT_CONNECT_WILL | MQTT_CONNECT_WILL_QOS_2.

It should be noted that the following flags are the only flags that need to be set explicitly:

• MQTT_CONNECT_CLEAN_SESSION
• MQTT_CONNECT_WILL_QOS_X
• MQTT_CONNECT_WILL_RETAIN

All the other flags are automatically determined based on the arguments to mqtt_connect (for example if the user_name argument is not NULL then MQTT-C will automatically set MQTT_CONNECT_USER_NAME). This means that in the multi-flag example given above the MQTT_CONNECT_WILL is not mandatory as is automatically set when will_topic and will_message are not NULL.

Does this clarify things?

Regards,

Liam

from mqtt-c.