Type Definition paho_mqtt_sys::MQTTAsync_traceCallback

type MQTTAsync_traceCallback = Option<unsafe extern "C" fn(level: MQTTASYNC_TRACE_LEVELS, message: *mut c_char)>;

This is a callback function prototype which must be implemented if you want to receive trace information. @param level the trace level of the message returned @param message the trace message. This is a pointer to a static buffer which will be overwritten on each call. You must copy the data if you want to keep it for later.