Type Definition paho_mqtt3as_sys::MQTTAsync_traceCallback

type MQTTAsync_traceCallback = Option<unsafe extern "C" fn(_: MQTTASYNC_TRACE_LEVELS, _: *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 meesage 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.