Mosquitto - subscribe to one broker and push to another using C

Is it possible and if so how to archive it that one application using libmosquitto get messages from one broker and publish it to another?

Its pretty simple to just change topic in mosquito_publish function, but set of broker takes place in

mosquitto_connect(mosq, "localhost",1883 , 60); 

Running mosquitto_connet second time e.g.

 mosquitto_connect(mosq, "mqtt.example.io",1883 , 60); 

ends up connecting to last one.

I tried to create two mosquitto structs but I dont know how to inform second one about message form subbed channel in order to get info from it, change it and push to proper broker.

Something like this should do the job (I've not tested it though). You'll have to add error checking.

#include <stdio.h>
#include <mosquitto.h>


void on_connect1(struct mosquitto *mosq, void *obj, int result)
{
    int rc = MOSQ_ERR_SUCCESS;

    if(!result){
        mosquitto_subscribe(mosq, NULL, "/v1/topic1", 0);
    }else{
        fprintf(stderr, "%s\n", mosquitto_connack_string(result));
    }
}

void on_message1(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
{
    struct mosquitto *mosq2 = (struct mosquitto *)obj;

    mosquitto_publish(mosq, NULL, "/v1/topic2", message->payloadlen, message->payload, message->qos, message->retain);
}

int main(int argc, char *argv[])
{
    struct mosquitto *mosq1, *mosq2;

    mosquitto_lib_init();

    mosq2 = mosquitto_new(NULL, true, NULL);
    mosq1 = mosquitto_new(NULL, true, mosq2);

    mosquitto_connect_callback_set(mosq1, on_connect1);
    mosquitto_message_callback_set(mosq1, on_message1);

    mosquitto_connect(mosq2, "mqtt.example.io", 1883, 60);
    mosquitto_connect(mosq1, "localhost", 1883, 60);

    mosquitto_loop_start(mosq2);
    mosquitto_loop_forever(mosq1, -1, 1);

    mosquitto_destroy(mosq1);
    mosquitto_destroy(mosq2);

    mosquitto_lib_cleanup();

    return 0;
}