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Cloud Lee
Cloud Lee

Reputation: 31

Paho mqtt client got connection lost

I have a little problem about paho mqtt library. I register a callback function MQTTClient_messageArrived and MQTTClient_connectionLost.

And I call MQTTClient_subscribe() or MQTTClient_unsubscribe() in this callback function. After running this callback function. I got a error code (-3) from MQTTClient_connectionLost. Furthermore, I print the cause is NULL.

Is any possible problem to my problem? Thanks

Here are my initialize function and callback function:

void mqtt_initialize(void){
    int rc;

    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;

    if(MQTTClient_create(&g_MQTT_client, BROKER_ADDR, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL) < 0){
        g_mqtt_exist = MQTT_INSTANCE_NOT_EXIST;
    } else {
        g_mqtt_exist = MQTT_INSTANCE_EXIST;
    }

    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;

    MQTTClient_setCallbacks(g_MQTT_client, NULL, mqtt_connlost_cb, mqtt_arrived_cb, mqtt_delivered_cb);

    if ((rc = MQTTClient_connect(g_MQTT_client, &conn_opts)) != MQTTCLIENT_SUCCESS) {
        MAIN_PRINT_DEBUG(0, "Failed to connect MQTT broker, return code %d\n", rc);
        mqtt_free();
    } 

    /* set subscribe control topic */
    MQTTClient_subscribe(g_MQTT_client, "topic_1", MQTT_QOS);
}


int mqtt_arrived_cb(void *context, char *topicName, int topicLen, MQTTClient_message *message)
{
    int ret = 0;
    printf("topic: %s\n", topicName);
    if(!strcmp(topicName, "topic_1")){
        printf("topic_1\n");
        ret = MQTTClient_subscribe(g_MQTT_client, "topic_2", 0);
        if (ret < 0){
            printf("mqtt operation fail\n");
        }       
    } 
    return 1;

}

void mqtt_connlost_cb(void *context, char *cause)
{
    MAIN_PRINT_DEBUG(0, "\n MQTT Connection lost\n");
    MAIN_PRINT_DEBUG(0,"     cause: %s\n", cause);
}

Upvotes: 0

Views: 6867

Answers (1)

Java dev
Java dev

Reputation: 535

Did you try connecting any other client to same broker with same client id? That could be a possible case if you are getting connection lost. Also if your callback throws exception, it will cause connection lost, however in this case paho will reconnect.

Upvotes: 0

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