Connect to Beebotte using Paho MQTT C client - with encryption

subsriber.c

/**
 * to compile this code
 * cc -g -o subscriber subscriber.c -lpaho-mqtt3cs -lpthread
 **/
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "MQTTClient.h"

// set protocol to ssl and port number to 8883 to use encryption
#define ADDRESS     "ssl://mqtt.beebotte.com:8883"
#define TOPIC       "test/test"
#define CLIENTID    "my_device_identifier"
#define QOS         1
#define TIMEOUT     10000L

volatile MQTTClient_deliveryToken deliveredtoken;

void delivered(void *context, MQTTClient_deliveryToken dt)
{
    printf("Message with token value %d delivery confirmed\n", dt);
    deliveredtoken = dt;
}

int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)
{
    int i;
    char* payloadptr;

    printf("Message arrived\n");
    printf("     topic: %s\n", topicName);
    printf("   message: ");

    payloadptr = message->payload;
    for(i=0; i<message->payloadlen; i++)
    {
        putchar(*payloadptr++);
    }
    putchar('\n');
    MQTTClient_freeMessage(&message);
    MQTTClient_free(topicName);
    return 1;
}

void connlost(void *context, char *cause)
{
    printf("\nConnection lost\n");
    printf("     cause: %s\n", cause);
}

int main(int argc, char* argv[])
{
    MQTTClient client;
    
    //Initialize connection options
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    
    //Initialize SSL options
    MQTTClient_SSLOptions sslopts = MQTTClient_SSLOptions_initializer;

    int rc;
    int ch;

    MQTTClient_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    conn_opts.username = "token:YOUR_CHANNEL_TOKEN";
    
    //get the server certificate from beebotte.com/certs/mqtt.beebotte.com.pem
    sslopts.trustStore="mqtt.beebotte.com.pem";
    //enable server certificate validation
    sslopts.enableServerCertAuth = 1;
    
    //set SSL options in connection options
    conn_opts.ssl = &sslopts;
    
    //Set callbacks
    MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered);

    //Connect
    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        printf("Failed to connect, return code %d\n", rc);
        exit(-1);
    }
    
    printf("Subscribing to topic %s\n using QoS%d\n\n"
           "Press Q<Enter> to quit\n\n", TOPIC, QOS);

    //Subscribe
    MQTTClient_subscribe(client, TOPIC, QOS);

    do
    {
        ch = getchar();
    } while(ch!='Q' && ch != 'q');

    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);
    return rc;
}