EMQX安装及简单的发布订阅

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已于 2024-05-31 13:21:25 修改

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于 2024-05-30 15:36:51 首次发布

本文链接：https://blog.youkuaiyun.com/qq_41846388/article/details/139324940

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Centos7下安装EMQX

yum 安装

#下载rpm包
wget https://www.emqx.com/zh/downloads/broker/5.6.1/emqx-5.6.1-el7-amd64.rpm
#安装
yum install emqx-5.6.1-el7-amd64.rpm -y
#启动
systemctl start emqx
#停止
systemctl stop emqx
#查看状态
systemctl status emqx
#重启
systemctl restart emqx

压缩包安装

#下载压缩包
wget https://www.emqx.com/zh/downloads/broker/5.7.0/emqx-5.7.0-el7-amd64.tar.gz
#安装d
mkdir -p emqx && tar -zxvf emqx-5.7.0-el7-amd64.tar.gz -C emqx
#启动
./emqx/bin/emqx start
#停止
./emqx/bin/emqx stop

现在您可通过浏览器访问 http://localhost:18083/（localhost 可替换为您的实际 IP 地址）以访问 EMQX Dashboard 管理控制台，进行设备连接与相关指标监控管理。

默认用户名及密码：
admin
public

在 Java 中使用 MQTT

构建工具：Maven
IDE：IntelliJ IDEA
Java 版本：JDK 1.8.0
本文将使用 Eclipse Paho Java Client 作为客户端，该客户端是 Java 语言中使用最为广泛的 MQTT 客户端库。
添加以下依赖到项目 pom.xml 文件中。

<dependencies>
   <dependency>
       <groupId>org.eclipse.paho</groupId>
       <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
       <version>1.2.5</version>
   </dependency>
</dependencies>

发布 MQTT 消息

创建一个发布客户端类 PublishSample，该类将发布一条 Hello MQTT 消息至主题 mqtt/test

package io.emqx.mqtt;

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class PublishSample {

   public static void main(String[] args) {

       String broker = "tcp://broker.emqx.io:1883";
       String topic = "mqtt/test";
       String username = "emqx";
       String password = "public";
       String clientid = "publish_client";
       String content = "Hello MQTT";
       int qos = 0;

       try {
           MqttClient client = new MqttClient(broker, clientid, new MemoryPersistence());
           // 连接参数
           MqttConnectOptions options = new MqttConnectOptions();
           // 设置用户名和密码
           options.setUserName(username);
           options.setPassword(password.toCharArray());
           options.setConnectionTimeout(60);
      options.setKeepAliveInterval(60);
           // 连接
           client.connect(options);
           // 创建消息并设置 QoS
           MqttMessage message = new MqttMessage(content.getBytes());
           message.setQos(qos);
           // 发布消息
           client.publish(topic, message);
           System.out.println("Message published");
           System.out.println("topic: " + topic);
           System.out.println("message content: " + content);
           // 关闭连接
           client.disconnect();
           // 关闭客户端
           client.close();
      } catch (MqttException e) {
           throw new RuntimeException(e);
      }
  }
}

订阅 MQTT 主题

创建一个订阅客户端类 SubscribeSample，该类将订阅主题 mqtt/test

package io.emqx.mqtt;

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class SubscribeSample {
   public static void main(String[] args) {
       String broker = "tcp://broker.emqx.io:1883";
       String topic = "mqtt/test";
       String username = "emqx";
       String password = "public";
       String clientid = "subscribe_client";
       int qos = 0;

       try {
           MqttClient client = new MqttClient(broker, clientid, new MemoryPersistence());
           // 连接参数
           MqttConnectOptions options = new MqttConnectOptions();
           options.setUserName(username);
           options.setPassword(password.toCharArray());
           options.setConnectionTimeout(60);
      options.setKeepAliveInterval(60);
           // 设置回调
           client.setCallback(new MqttCallback() {
				//连接丢失时被调用
               public void connectionLost(Throwable cause) {
                   System.out.println("connectionLost: " + cause.getMessage());
              }
				//接收到消息时被调用
               public void messageArrived(String topic, MqttMessage message) {
                   System.out.println("topic: " + topic);
                   System.out.println("Qos: " + message.getQos());
                   System.out.println("message content: " + new String(message.getPayload()));

              }
				//消息发送完成时被调用
               public void deliveryComplete(IMqttDeliveryToken token) {
                   System.out.println("deliveryComplete---------" + token.isComplete());
              }

          });
           client.connect(options);
           client.subscribe(topic, qos);
      } catch (Exception e) {
           e.printStackTrace();
      }
  }
}