subasync − Asynchronous subscription example
#include
<stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#define ADDRESS
"tcp://mqtt.eclipseprojects.io:1883"
#define CLIENTID "ExampleClientSub"
#define TOPIC "MQTT Examples"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
volatile MQTTClient_deliveryToken deliveredtoken;
void
delivered(void *context, MQTTClient_deliveryToken dt)
{
printf("Message with token value %d delivery
confirmed0, dt);
deliveredtoken = dt;
}
int
msgarrvd(void *context, char *topicName, int topicLen,
MQTTClient_message *message)
{
printf("Message arrived0);
printf(" topic: %s0, topicName);
printf(" message: %.*s0, message->payloadlen,
(char*)message->payload);
MQTTClient_freeMessage(&message);
MQTTClient_free(topicName);
return 1;
}
void
connlost(void *context, char *cause)
{
printf("1onnection lost0);
printf(" cause: %s0, cause);
}
int main(int
argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts =
MQTTClient_connectOptions_initializer;
int rc;
if ((rc =
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to create client, return code %d0, rc);
rc = EXIT_FAILURE;
goto exit;
}
if ((rc =
MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd,
delivered)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to set callbacks, return code %d0, rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
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);
rc = EXIT_FAILURE;
goto destroy_exit;
}
printf("Subscribing
to topic %s0or client %s using QoS%d0
"Press Q<Enter> to quit0, TOPIC, CLIENTID, QOS);
if ((rc = MQTTClient_subscribe(client, TOPIC, QOS)) !=
MQTTCLIENT_SUCCESS)
{
printf("Failed to subscribe, return code %d0, rc);
rc = EXIT_FAILURE;
}
else
{
int ch;
do
{
ch = getchar();
} while (ch!=’Q’ && ch !=
’q’);
if ((rc =
MQTTClient_unsubscribe(client, TOPIC)) !=
MQTTCLIENT_SUCCESS)
{
printf("Failed to unsubscribe, return code %d0, rc);
rc = EXIT_FAILURE;
}
}
if ((rc =
MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to disconnect, return code %d0, rc);
rc = EXIT_FAILURE;
}
destroy_exit:
MQTTClient_destroy(&client);
exit:
return rc;
}