Mosquitto publisher not publishing integers in C - c

Question

I'm using Paho client libraries for C to write a client which publishes an integer to the mosquitto broker. When i set the payload as a string, it publishes with no problems, but when i set the payload to be an integer, the publisher crashes with the following message as shown in the image.
My client code is as follows:
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "MQTTClient.h"
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ExampleClientPub"
#define TOPIC "MQTT Examples"
#define QOS 1
#define TIMEOUT 10000L
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc, ch;
int i = 4;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.username = "user";
conn_opts.password = "hello";
conn_opts.keepAliveInterval = 65000;
conn_opts.cleansession = 1;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(-1);
}
pubmsg.payload = i;
pubmsg.payloadlen = sizeof(i); //strlen(PAYLOAD);
pubmsg.qos = QOS;
pubmsg.retained = 0;
MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
printf("Waiting for up to %d seconds for publication of %d\n"
"on topic %s for client with ClientID: %s\n",
(int)(TIMEOUT / 1000), i, TOPIC, CLIENTID);
rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
printf("Message with delivery token %d delivered\n", token);
do
{
ch = getchar();
} while (ch != 'Q' && ch != 'q');
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}
Can anyone please tell me what I'm doing wrong?

Answer 1

The type of payload is char *
typedef struct {
char * topic;
char * payload;
unsigned int length;
boolean retained;
} MQTTMessage;
That means it only accepts strings.

Answer 2

In case somebody comes across this post, this works for me:
Publish as:
uint32_t mmsg = (2<<31)-1;
mosquitto_publish(mosq, NULL, "topic\0", 4, &mmsg, 2, false);
Read As
LOGD("Message topic and load are %s and %lu\n ", msg->topic, *((uint32_t *) (msg->payload)));
LOGD is just a macro around fprintf(stdout, ....)

Answer 3

The payload field of MQTTClient_message is a char *, you need to use a pointer and to cast it properly if you want to send an integer:
pubmsg.payload = (char *)(&i);