1、只有异步接口 MQTTAsync中才有，使用起来不是特别方便
2、需要配置参数
conn_opts.automaticReconnect = 1;
conn_opts.minRetryInterval = 2;
conn_opts.maxRetryInterval = 365*24*60*60;
3、需要配置函数
if ((rc = MQTTAsync_setConnected(client, client, onReconnected)) != MQTTASYNC_SUCCESS)
{
printf("Failed to MQTTAsync_setConnected, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
4、连接成功后的回调实现
void onReconnected(void* context, char* cause)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
int rc;
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
int rc;
printf("Successful reconnection\n");
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
opts.onSuccess = onSubscribe;
opts.onFailure = onSubscribeFailure;
opts.context = client;
if ((rc = MQTTAsync_subscribe(client, TOPIC, QOS, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start subscribe, return code %d\n", rc);
finished = 1;
}
}
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
opts.onSuccess = onSubscribe;
opts.onFailure = onSubscribeFailure;
opts.context = client;
if ((rc = MQTTAsync_subscribe(client, TOPIC, QOS, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start subscribe, return code %d\n", rc);
finished = 1;
}
}
/*******************************************************************************
* Copyright (c) 2012, 2020 IBM Corp.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v2.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
* https://www.eclipse.org/legal/epl-2.0/
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Ian Craggs - initial contribution
*******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTAsync.h"
#if !defined(_WIN32)
#include <unistd.h>
#else
#include <windows.h>
#endif
#if defined(_WRS_KERNEL)
#include <OsWrapper.h>
#endif
#define ADDRESS "tcp://mqtt.eclipse.org:1883"
#define CLIENTID "ExampleClientSub"
#define TOPIC "MQTT Examples"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
int disc_finished = 0;
int subscribed = 0;
int finished = 0;
void connlost(void *context, char *cause)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
int rc;
printf("\nConnection lost\n");
if (cause)
printf(" cause: %s\n", cause);
printf("Reconnecting\n");
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start connect, return code %d\n", rc);
finished = 1;
}
}
int msgarrvd(void *context, char *topicName, int topicLen, MQTTAsync_message *message)
{
printf("Message arrived\n");
printf(" topic: %s\n", topicName);
printf(" message: %.*s\n", message->payloadlen, (char*)message->payload);
MQTTAsync_freeMessage(&message);
MQTTAsync_free(topicName);
return 1;
}
void onDisconnectFailure(void* context, MQTTAsync_failureData* response)
{
printf("Disconnect failed, rc %d\n", response->code);
disc_finished = 1;
}
void onDisconnect(void* context, MQTTAsync_successData* response)
{
printf("Successful disconnection\n");
disc_finished = 1;
}
void onSubscribe(void* context, MQTTAsync_successData* response)
{
printf("Subscribe succeeded\n");
subscribed = 1;
}
void onSubscribeFailure(void* context, MQTTAsync_failureData* response)
{
printf("Subscribe failed, rc %d\n", response->code);
finished = 1;
}
void onConnectFailure(void* context, MQTTAsync_failureData* response)
{
printf("Connect failed, rc %d\n", response->code);
finished = 1;
}
void onConnect(void* context, MQTTAsync_successData* response)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
int rc;
printf("Successful connection\n");
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
opts.onSuccess = onSubscribe;
opts.onFailure = onSubscribeFailure;
opts.context = client;
if ((rc = MQTTAsync_subscribe(client, TOPIC, QOS, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start subscribe, return code %d\n", rc);
finished = 1;
}
}
void onReconnected(void* context, char* cause)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
int rc;
printf("Successful reconnection\n");
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
opts.onSuccess = onSubscribe;
opts.onFailure = onSubscribeFailure;
opts.context = client;
if ((rc = MQTTAsync_subscribe(client, TOPIC, QOS, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start subscribe, return code %d\n", rc);
finished = 1;
}
}
int main(int argc, char* argv[])
{
MQTTAsync client;
MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
MQTTAsync_disconnectOptions disc_opts = MQTTAsync_disconnectOptions_initializer;
int rc;
int ch;
if ((rc = MQTTAsync_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL))
!= MQTTASYNC_SUCCESS)
{
printf("Failed to create client, return code %d\n", rc);
rc = EXIT_FAILURE;
goto exit;
}
if ((rc = MQTTAsync_setCallbacks(client, client, connlost, msgarrvd, NULL)) != MQTTASYNC_SUCCESS)
{
printf("Failed to set callbacks, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
if ((rc = MQTTAsync_setConnected(client, client, onReconnected)) != MQTTASYNC_SUCCESS)
{
printf("Failed to MQTTAsync_setConnected, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
conn_opts.onSuccess = onConnect;
conn_opts.onFailure = onConnectFailure;
conn_opts.context = client;
conn_opts.automaticReconnect = 1;
conn_opts.minRetryInterval = 2; //seconds
conn_opts.maxRetryInterval = 365*24*60*60;
if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start connect, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
while (!subscribed && !finished)
#if defined(_WIN32)
Sleep(100);
#else
usleep(10000L);
#endif
if (finished)
goto exit;
do
{
ch = getchar();
} while (ch!='Q' && ch != 'q');
disc_opts.onSuccess = onDisconnect;
disc_opts.onFailure = onDisconnectFailure;
if ((rc = MQTTAsync_disconnect(client, &disc_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start disconnect, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
while (!disc_finished)
{
#if defined(_WIN32)
Sleep(100);
#else
usleep(10000L);
#endif
}
destroy_exit:
MQTTAsync_destroy(&client);
exit:
return rc;
}
