When connecting using MQTTv5, Mosquitto does not automatically reconnect after the first connection failure.

[wrwcwq]

I am using Mosquitto version 2.0.18 for MQTT connections. When using MQTTv5, if the initial connection attempt fails, Mosquitto does not automatically attempt a reconnection. The initialization code is as follows:

`char sn[64] = {0};
mqtt_prop_sn_get(NULL, sn, sizeof(sn));
g_mosq = mosquitto_new(sn, true, NULL);
if (!g_mosq)
{
MOCAR_LOG_ERROR("create client fail");
return -1;
}
mosquitto_int_option(g_mosq, MOSQ_OPT_PROTOCOL_VERSION, MQTT_PROTOCOL_V5);
int loop = mosquitto_loop_start(g_mosq);
if (loop != MOSQ_ERR_SUCCESS)
{
MOCAR_LOG_ERROR_FMT("mosquitto loop error");
huali_plf_mqtt_cleanup();
return -1;
}
mosquitto_username_pw_set(mosq, g_mqtt_info.user_id, g_mqtt_info.password);
mosquitto_connect_v5_callback_set(mosq, my_connect_v5_callback);
mosquitto_message_v5_callback_set(mosq, my_message_v5_callback);
mosquitto_subscribe_v5_callback_set(mosq, my_subscribe_v5_callback);
mosquitto_disconnect_v5_callback_set(mosq, my_disconnect_v5_callback);
mosquitto_reconnect_delay_set(mosq, 5, 15, true);

while (1)
{
ret = mosquitto_connect_async(g_mosq, mqtt_info.address, mqtt_info.port, KEEP_ALIVE);
if (MOSQ_ERR_SUCCESS == ret)
{
MOCAR_LOG_DEBUG_FMT("mosquitto_connect_async success");
break;
}
else if (MOSQ_ERR_INVAL == ret)
{
MOCAR_LOG_DEBUG_FMT("the input parameters were invalid");
break;
}
else
{
MOCAR_LOG_DEBUG_FMT("mqtt connect failed: %s", strerror(errno));
sleep(3);
continue;
}
}
`
Later, I attempted to use a timer to manually reconnect every 30 seconds, which successfully reestablishes the connection. However, it results in an 8MB memory leak issue each time mosquitto_loop_start is called. Here is my reconnection code:

void mqtt_check_reconnect(void) { if (1 != cv2x_plf_mqtt_get_send_flag()) { int rc = 0; mosquitto_disconnect(g_mosq); mosquitto_loop_stop(g_mosq, true); sleep(1); mosquitto_username_pw_set(g_mosq, g_mqtt_info.user_id, g_mqtt_info.password); cv2x_plf_mqtt_connect_handle(); rc = mosquitto_loop_start(g_mosq); if (rc) { MOCAR_LOG_ERROR_FMT("mosquitto_loop_start failed, rc is %s", mosquitto_strerror(rc)); return; } } }

[wrwcwq]

The problem has been identified. In the mosquitto__thread_main function, the value of mosq->threaded is set to mosq_ts_none, which directly causes mosquitto_loop_stop to return because mosq->threaded != mosq_ts_self, and thread-related operations are not performed.

To modify the Mosquitto source code, you can comment out the line that sets mosq->threaded to mosq_ts_none, like this:
`void *mosquitto__thread_main(void *obj)
{
struct mosquitto *mosq = obj;
#ifndef WIN32
struct timespec ts;
ts.tv_sec = 0;
ts.tv_nsec = 10000000;
#endif

if(!mosq) return NULL;

do{
	if(mosquitto__get_state(mosq) == mosq_cs_new){

#ifdef WIN32
Sleep(10);
#else
nanosleep(&ts, NULL);
#endif
}else{
break;
}
}while(1);

if(!mosq->keepalive){
	/* Sleep for a day if keepalive disabled. */
	mosquitto_loop_forever(mosq, 1000*86400, 1);
}else{
	/* Sleep for our keepalive value. publish() etc. will wake us up. */
	mosquitto_loop_forever(mosq, mosq->keepalive*1000, 1);
}
// if(mosq->threaded == mosq_ts_self){
// 	mosq->threaded = mosq_ts_none;
// }

return obj;

}`