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pubsync ā€” Synchronous publication example

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"

#define ADDRESS     "tcp://mqtt.eclipse.org:1883"
#define CLIENTID    "ExampleClientPub"
#define TOPIC       "MQTT Examples"
#define PAYLOAD     "Hello World!"
#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;

    if ((rc = MQTTClient_create(&client, ADDRESS, CLIENTID,
        MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS)
    {
         printf("Failed to create client, return code %d0, rc);
         exit(EXIT_FAILURE);
    }

    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        printf("Failed to connect, return code %d0, rc);
        exit(EXIT_FAILURE);
    }

    pubmsg.payload = PAYLOAD;
    pubmsg.payloadlen = (int)strlen(PAYLOAD);
    pubmsg.qos = QOS;
    pubmsg.retained = 0;
    if ((rc = MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token)) != MQTTCLIENT_SUCCESS)
    {
         printf("Failed to publish message, return code %d0, rc);
         exit(EXIT_FAILURE);
    }

    printf("Waiting for up to %d seconds for publication of %s0
            "on topic %s for client with ClientID: %s0,
            (int)(TIMEOUT/1000), PAYLOAD, TOPIC, CLIENTID);
    rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
    printf("Message with delivery token %d delivered0, token);

    if ((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS)
        printf("Failed to disconnect, return code %d0, rc);
    MQTTClient_destroy(&client);
    return rc;
}

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Tue Sep 14 2021 Paho MQTT C Client Library