JAVA开发MQTT总结

Posted 2021-03-07 rain1024

JAVA开发MQTT总结

MQTT 介绍

• 它是一种 机器之间通讯 machine-to-machine (M2M)、物联网 Internet of Things （IoT）常用的一种轻量级消息传输协议
• 适用于网络带宽较低的场合
• 包含发布、订阅模式，通过一个代理服务器（broker），任何一个客户端（client）都可以订阅或者发布某个主题的消息，然后订阅了该主题的客户端则会收到该消息

mqtt还是之前公司有需求所以写的一个demo，在这里记录下来，方便有人使用的时候查阅，不涉及mqtt的具体讲解，只是贴代码和运行过程。

MQTT的入门，以及特性，协议，结构的讲解，请看下面这篇文章

https://www.runoob.com/w3cnote/mqtt-intro.html

什么是MQTT，它能干什么，它的应用场景在哪里？请参考下面这篇文章

https://www.ibm.com/developerworks/cn/iot/iot-mqtt-why-good-for-iot/index.html

本文中采用的MQTT服务器Apache-Apollo的下载配置搭建过程，请参考下面这篇文章

https://blog.csdn.net/qq_29350001/article/details/76680646

下面就开始创建broker，

RaindeMacBook-Pro:bin rain$ ./apollo create mybroker
Creating apollo instance at: mybroker
Generating ssl keystore...

Warning:
JKS 密钥库使用专用格式。建议使用 "keytool -importkeystore -srckeystore keystore -destkeystore keystore -deststoretype pkcs12" 迁移到行业标准格式 PKCS12。

You can now start the broker by executing:

   "/Users/rain/Documents/Soft/apache-apollo-1.7.1/bin/mybroker/bin/apollo-broker" run

Or you can run the broker in the background using:

   "/Users/rain/Documents/Soft/apache-apollo-1.7.1/bin/mybroker/bin/apollo-broker-service" start

进入新生成的broker中

RaindeMacBook-Pro:bin rain$ ls
apollo      apollo.cmd  mybroker    testbroker
RaindeMacBook-Pro:bin rain$ cd mybroker/
RaindeMacBook-Pro:mybroker rain$ ls
bin data    etc log tmp
RaindeMacBook-Pro:mybroker rain$ cd bin
RaindeMacBook-Pro:bin rain$ ls
apollo-broker       apollo-broker-service

可以看到有两个文件，启动apollo-broker

启动成功以后，就可以在浏览器中访问了，默认用户名和密码是admin，password

刚进去是，Topics选项卡是空的，我是在运行程序后截图的，所以有一个topic列表

配置Maven

在pom.xml中添加以下配置

<dependency>
            <groupId>org.eclipse.paho</groupId>
            <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
            <version>1.2.0</version>
        </dependency>

再创建下面的类

MqttServer

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

public class MqttServer2 {
    /**
     * 代理服务器ip地址
     */
    public static final String MQTT_BROKER_HOST = "tcp://127.0.0.1:61613";

    /**
     * 订阅标识
     */
    public static final String MQTT_TOPIC = "test2";

    private static String userName = "admin";
    private static String password = "password";

    /**
     * 客户端唯一标识
     */
    public static final String MQTT_CLIENT_ID = "android_server_xiasuhuei32";
    private static MqttTopic topic;
    private static MqttClient client;

    public static void main(String... args) {
        // 推送消息
        MqttMessage message = new MqttMessage();
        try {
            client = new MqttClient(MQTT_BROKER_HOST, MQTT_CLIENT_ID, new MemoryPersistence());
            MqttConnectOptions options = new MqttConnectOptions();
            options.setCleanSession(true);
            options.setUserName(userName);
            options.setPassword(password.toCharArray());
            options.setConnectionTimeout(10);
            options.setKeepAliveInterval(20);

            topic = client.getTopic(MQTT_TOPIC);

            message.setQos(1);
            message.setRetained(false);
            message.setPayload("message from server222222".getBytes());
            client.connect(options);

            while (true) {
                MqttDeliveryToken token = topic.publish(message);
                token.waitForCompletion();
                System.out.println("已经发送222");
                Thread.sleep(10000);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

MqttClient

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

public class MyMqttClient {
    /**
     * 代理服务器ip地址
     */
    public static final String MQTT_BROKER_HOST = "tcp://127.0.0.1:61613";

    /**
     * 客户端唯一标识
     */
    public static final String MQTT_CLIENT_ID = "android_xiasuhuei321";

    /**
     * 订阅标识
     */
//    public static final String MQTT_TOPIC = "xiasuhuei321";

    /**
     *
     */
    public static final String USERNAME = "admin";
    /**
     * 密码
     */
    public static final String PASSWORD = "password";
    public static final String TOPIC_FILTER = "test2";

    private volatile static MqttClient mqttClient;
    private static MqttConnectOptions options;

    public static void main(String... args) {
        try {
            // host为主机名，clientid即连接MQTT的客户端ID，一般以客户端唯一标识符表示，
            // MemoryPersistence设置clientid的保存形式，默认为以内存保存

            mqttClient = new MqttClient(MQTT_BROKER_HOST, MQTT_CLIENT_ID, new MemoryPersistence());
            // 配置参数信息
            options = new MqttConnectOptions();
            // 设置是否清空session,这里如果设置为false表示服务器会保留客户端的连接记录，
            // 这里设置为true表示每次连接到服务器都以新的身份连接
            options.setCleanSession(true);
            // 设置用户名
            options.setUserName(USERNAME);
            // 设置密码
            options.setPassword(PASSWORD.toCharArray());
            // 设置超时时间 单位为秒
            options.setConnectionTimeout(10);
            // 设置会话心跳时间 单位为秒 服务器会每隔1.5*20秒的时间向客户端发送个消息判断客户端是否在线，但这个方法并没有重连的机制
            options.setKeepAliveInterval(20);
            // 连接
            mqttClient.connect(options);
            // 订阅
            mqttClient.subscribe(TOPIC_FILTER);
            // 设置回调
            mqttClient.setCallback(new MqttCallback() {
                @Override
                public void connectionLost(Throwable throwable) {
                    System.out.println("connectionLost");
                }

                @Override
                public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
                    System.out.println("Topic: " + s + " Message: " + mqttMessage.toString());
                }

                @Override
                public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {

                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}

PublishSample

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;

/**
 *发布端
 */
public class PublishSample {
    public static void main(String[] args) {

        String topic = "test2";
        String content = "hello 哈哈";
        int qos = 1;
        String broker = "tcp://127.0.0.1:61613";
        String userName = "admin";
        String password = "password";
        String clientId = "pubClient";
        // 内存存储
        MemoryPersistence persistence = new MemoryPersistence();

        try {
            // 创建客户端
            MqttClient sampleClient = new MqttClient(broker, clientId, persistence);
            // 创建链接参数
            MqttConnectOptions connOpts = new MqttConnectOptions();
            // 在重新启动和重新连接时记住状态
            connOpts.setCleanSession(false);
            // 设置连接的用户名
            connOpts.setUserName(userName);
            connOpts.setPassword(password.toCharArray());
            // 建立连接
            sampleClient.connect(connOpts);
            // 创建消息
            MqttMessage message = new MqttMessage(content.getBytes());
            // 设置消息的服务质量
            message.setQos(qos);
            // 发布消息
            sampleClient.publish(topic, message);
            // 断开连接
            sampleClient.disconnect();
            // 关闭客户端
            sampleClient.close();
        } 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);
            me.printStackTrace();
        }
    }
}

SubscribeSample

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

/**
 *订阅端
 */
public class SubscribeSample {

    public static void main(String[] args) throws MqttException {
        String HOST = "tcp://127.0.0.1:61613";
        String TOPIC = "test2";
        int qos = 1;
        String clientid = "subClient";
        String userName = "admin";
        String passWord = "password";
        try {
            // host为主机名，test为clientid即连接MQTT的客户端ID，一般以客户端唯一标识符表示，MemoryPersistence设置clientid的保存形式，默认为以内存保存
            MqttClient client = new MqttClient(HOST, clientid, new MemoryPersistence());
            // MQTT的连接设置
            MqttConnectOptions options = new MqttConnectOptions();
            // 设置是否清空session,这里如果设置为false表示服务器会保留客户端的连接记录，这里设置为true表示每次连接到服务器都以新的身份连接
            options.setCleanSession(true);
            // 设置连接的用户名
            options.setUserName(userName);
            // 设置连接的密码
            options.setPassword(passWord.toCharArray());
            // 设置超时时间 单位为秒
            options.setConnectionTimeout(10);
            // 设置会话心跳时间 单位为秒 服务器会每隔1.5*20秒的时间向客户端发送个消息判断客户端是否在线，但这个方法并没有重连的机制
            options.setKeepAliveInterval(20);
            // 设置回调函数
            client.setCallback(new MqttCallback() {

                public void connectionLost(Throwable cause) {
                    System.out.println("connectionLost");
                }

                public void messageArrived(String topic, MqttMessage message) throws Exception {
                    System.out.println("topic:"+topic);
                    System.out.println("Qos:"+message.getQos());
                    System.out.println("message content:"+new String(message.getPayload()));

                }

                public void deliveryComplete(IMqttDeliveryToken token) {
                    System.out.println("deliveryComplete---------"+ token.isComplete());
                }

            });
            client.connect(options);
            //订阅消息
            client.subscribe(TOPIC, qos);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

启动程序

1.启动MqttServer2以后，开始循环发送消息。

2.启动MyMqttClient开始接收消息。

到这里，整个程序基本可以运行。

3.启动PublishSample，发布一条消息，在启动SubscribeSample来订阅发布的消息。

4.发布的消息在MyMqttClient中也会显示出来