Java 实现 MQTT 协议收发消息

使用 Java 与 mqttfx 工具，模拟 MQTT 通信

1、引入依赖

    <repositories>
        <repository>
            <id>Eclipse Paho Repo</id>
            <url>https://repo.eclipse.org/content/repositories/paho-snapshots/</url>
        </repository>
    </repositories>
    <dependency>
        <groupId>org.eclipse.paho</groupId>
        <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
        <version>1.2.1</version>
    </dependency>

2、Java 代码

package com.example.demo.iot;

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import java.util.Scanner;

/**
 * @author sugarppig
 * @date 2023/3/23 17:00
 */
public class MqttTest {
    
    
    public static void main(String[] args) {
    
    
        String broker = "tcp://mqtt.eclipseprojects.io:1883"; // MQTT代理的地址
        String clientId = "mqtt_java"; // 客户端ID
        MemoryPersistence persistence = new MemoryPersistence(); // 设置持久化
        try {
    
    
            MqttClient sampleClient = new MqttClient(broker, clientId, persistence);
            MqttConnectOptions connOpts = new MqttConnectOptions(); // 设置连接选项
            connOpts.setCleanSession(true); // 设置会话清除标志
            System.out.println("Connecting to broker: " + broker);
            sampleClient.connect(connOpts); // 连接到MQTT代理
            System.out.println("Connected");


            // 订阅MQTT FX的Topic
            String topic = "home/garden/fountain";
            int qos = 1;
            sampleClient.subscribe(topic, qos);
            System.out.println("Subscribed to topic: " + topic);

            // 接收来自MQTT FX的消息
            sampleClient.setCallback(new MqttCallback() {
    
    
                @Override
                public void messageArrived(String topic, MqttMessage message) throws Exception {
    
    
                    System.out.println("Received message: " + new String(message.getPayload()));
                }

                @Override
                public void connectionLost(Throwable cause) {
    
    
                    System.out.println("Connection lost: " + cause.getMessage());
                }

                @Override
                public void deliveryComplete(IMqttDeliveryToken token) {
    
    }
            });

            // 发布消息到MQTT FX的Topic
            System.out.println("Publishing message: ");
            Scanner scanner = new Scanner(System.in);
            while (scanner.hasNext()) {
    
    
                String content = scanner.nextLine();
                MqttMessage message = new MqttMessage(content.getBytes());
                message.setQos(qos);
                sampleClient.publish(topic, message);
            }

            //Thread.sleep(5000); // 等待5秒钟

            // 断开连接
            //sampleClient.disconnect();
            //System.out.println("Disconnected");

        } catch (MqttException me) {
    
    
            System.out.println("reason " + me.getReasonCode());
            System.out.println("msg " + me.getMessage());
            System.out.println("loc " + me.getLocalizedMessage());
            System.out.println("cause " + me.getCause());
            System.out.println("excep " + me);
        } catch (Exception e) {
    
    
            e.printStackTrace();
        }
    }
}

3、实现效果