MQTT的学习研究（4）moquette-mqtt 的使用之mqtt Blocking API客户端订阅并接收主题信息

MQTT的学习研究（四）moquette-mqtt 的使用之mqt Blocking API客户端订阅并接收主题信息

在上面两篇关于mqtt的broker的启动和mqtt的服务端发布主题信息之后，我们客户端需要订阅相关的信息并接收相关的主题信息。

package com.etrip.mqtt;

import java.net.URISyntaxException;

import org.fusesource.mqtt.client.BlockingConnection;
import org.fusesource.mqtt.client.MQTT;
import org.fusesource.mqtt.client.Message;
import org.fusesource.mqtt.client.QoS;
import org.fusesource.mqtt.client.Topic;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
*
* MQTT moquette 的Client 段用于订阅主题，并接收主题信息
*
* 采用阻塞式 订阅主题
*
* @author longgangbai
*/
public class MQTTClient {
private static final Logger LOG = LoggerFactory.getLogger(MQTTClient.class);
private final static String CONNECTION_STRING = "tcp://192.168.208.46:1883";
private final static boolean CLEAN_START = true;
private final static short KEEP_ALIVE = 30;// 低耗网络，但是又需要及时获取数据，心跳30s
private final static String CLIENT_ID = "publishService";
public  static Topic[] topics = {
new Topic("china/beijing", QoS.EXACTLY_ONCE),
new Topic("china/tianjin", QoS.AT_LEAST_ONCE),
new Topic("china/henan", QoS.AT_MOST_ONCE)};
public final  static long RECONNECTION_ATTEMPT_MAX=6;
public final  static long RECONNECTION_DELAY=2000;

public final static int SEND_BUFFER_SIZE=2*1024*1024;//发送最大缓冲为2M

public static void main(String[] args)   {
//创建MQTT对象
MQTT mqtt = new MQTT();
BlockingConnection connection=null;
try {
//设置mqtt broker的ip和端口
mqtt.setHost(CONNECTION_STRING);
//连接前清空会话信息
mqtt.setCleanSession(CLEAN_START);
//设置重新连接的次数
mqtt.setReconnectAttemptsMax(RECONNECTION_ATTEMPT_MAX);
//设置重连的间隔时间
mqtt.setReconnectDelay(RECONNECTION_DELAY);
//设置心跳时间
mqtt.setKeepAlive(KEEP_ALIVE);
//设置缓冲的大小
mqtt.setSendBufferSize(SEND_BUFFER_SIZE);

//获取mqtt的连接对象BlockingConnection
connection = mqtt.blockingConnection();
//MQTT连接的创建
connection.connect();
//创建相关的MQTT 的主题列表
Topic[] topics = {new Topic("china/beijing", QoS.AT_LEAST_ONCE)};
//订阅相关的主题信息
byte[] qoses = connection.subscribe(topics);
//
while(true){
//接收订阅的消息内容
Message message = connection.receive();
//获取订阅的消息内容
byte[] payload = message.getPayload();
// process the message then:
LOG.info("MQTTClient Message  Topic="+message.getTopic()+" Content :"+new String(payload));
//签收消息的回执
message.ack();

Thread.sleep(2000);
}
} catch (URISyntaxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
connection.disconnect();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}