package bsit.mqtt.demo.one_way; import org.eclipse.paho.client.mqttv3.MqttClient; import org.eclipse.paho.client.mqttv3.MqttConnectOptions; import org.eclipse.paho.client.mqttv3.MqttDeliveryToken; import org.eclipse.paho.client.mqttv3.MqttException; import org.eclipse.paho.client.mqttv3.MqttMessage; import org.eclipse.paho.client.mqttv3.MqttPersistenceException; import org.eclipse.paho.client.mqttv3.MqttTopic; import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence; /** * * Title:Server * Description: 服务器向多个客户端推送主题,即不同客户端可向服务器订阅相同主题 * @author chenrl * 2016年1月6日下午3:29:28 */ public class Server { public static final String HOST = "tcp://192.168.1.3:61613"; public static final String TOPIC = "toclient/124"; public static final String TOPIC125 = "toclient/125"; private static final String clientid = "server"; private MqttClient client; private MqttTopic topic; private MqttTopic topic125; private String userName = "admin"; private String passWord = "password"; private MqttMessage message; public Server() throws MqttException { // MemoryPersistence设置clientid的保存形式,默认为以内存保存 client = new MqttClient(HOST, clientid, new MemoryPersistence()); connect(); } private void connect() { MqttConnectOptions options = new MqttConnectOptions(); options.setCleanSession(false); options.setUserName(userName); options.setPassword(passWord.toCharArray()); // 设置超时时间 options.setConnectionTimeout(10); // 设置会话心跳时间 options.setKeepAliveInterval(20); try { client.setCallback(new PushCallback()); client.connect(options); topic = client.getTopic(TOPIC); topic125 = client.getTopic(TOPIC125); } catch (Exception e) { e.printStackTrace(); } } public void publish(MqttTopic topic , MqttMessage message) throws MqttPersistenceException, MqttException { MqttDeliveryToken token = topic.publish(message); token.waitForCompletion(); System.out.println("message is published completely! " + token.isComplete()); } public static void main(String[] args) throws MqttException { Server server = new Server(); server.message = new MqttMessage(); server.message.setQos(2); server.message.setRetained(true); server.message.setPayload("给客户端124推送的信息".getBytes()); server.publish(server.topic , server.message); server.message = new MqttMessage(); server.message.setQos(2); server.message.setRetained(true); server.message.setPayload("给客户端125推送的信息".getBytes()); server.publish(server.topic125 , server.message); System.out.println(server.message.isRetained() + "------ratained状态"); } }
客户端代码:
package bsit.mqtt.demo.one_way; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; 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.MqttSecurityException; import org.eclipse.paho.client.mqttv3.MqttTopic; import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence; public class Client { public static final String HOST = "tcp://192.168.1.3:61613"; public static final String TOPIC = "toclient/124"; private static final String clientid = "client124"; private MqttClient client; private MqttConnectOptions options; private String userName = "admin"; private String passWord = "password"; private ScheduledExecutorService scheduler; private void start() { try { // host为主机名,clientid即连接MQTT的客户端ID,一般以唯一标识符表示,MemoryPersistence设置clientid的保存形式,默认为以内存保存 client = new MqttClient(HOST, clientid, new MemoryPersistence()); // MQTT的连接设置 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 client.setCallback(new PushCallback()); MqttTopic topic = client.getTopic(TOPIC); //setWill方法,如果项目中需要知道客户端是否掉线可以调用该方法。设置最终端口的通知消息 options.setWill(topic, "close".getBytes(), 2, true); client.connect(options); //订阅消息 int[] Qos = {1}; String[] topic1 = {TOPIC}; client.subscribe(topic1, Qos); } catch (Exception e) { e.printStackTrace(); } } public static void main(String[] args) throws MqttException { Client client = new Client(); client.start(); } }
MQTT订阅回调类:
package bsit.mqtt.demo.one_way; import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken; import org.eclipse.paho.client.mqttv3.MqttCallback; import org.eclipse.paho.client.mqttv3.MqttMessage; /** * 发布消息的回调类 * * 必须实现MqttCallback的接口并实现对应的相关接口方法CallBack 类将实现 MqttCallBack。 * 每个客户机标识都需要一个回调实例。在此示例中,构造函数传递客户机标识以另存为实例数据。 * 在回调中,将它用来标识已经启动了该回调的哪个实例。 * 必须在回调类中实现三个方法: * * public void messageArrived(MqttTopic topic, MqttMessage message)接收已经预订的发布。 * * public void connectionLost(Throwable cause)在断开连接时调用。 * * public void deliveryComplete(MqttDeliveryToken token)) * 接收到已经发布的 QoS 1 或 QoS 2 消息的传递令牌时调用。 * 由 MqttClient.connect 激活此回调。 * */ public class PushCallback implements MqttCallback { public void connectionLost(Throwable cause) { // 连接丢失后,一般在这里面进行重连 System.out.println("连接断开,可以做重连"); } public void deliveryComplete(IMqttDeliveryToken token) { System.out.println("deliveryComplete---------" + token.isComplete()); } public void messageArrived(String topic, MqttMessage message) throws Exception { // subscribe后得到的消息会执行到这里面 System.out.println("接收消息主题 : " + topic); System.out.println("接收消息Qos : " + message.getQos()); System.out.println("接收消息内容 : " + new String(message.getPayload())); } }
运行服务端代码,可看到服务器会给客户端124/125各推送一条消息,
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在运行124客户端代码,可看到124客户端接收的信息:
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然后把客户端代码的Topic改为TOPIC = "toclient/125";clientid = "client125";再运行该段代码,可看到125客户端接收的信息
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多个客户端订阅同一主题,其clientid必不相同。客户端124/125订阅各自主题的内容,但是不同时间启动,都在启动后接收到各自信息,这体现出了服务器的推送功能。同样的,发送的主题信息,可以在服务器的topic可以看到,访问路径是:http://127.0.0.1:61680/
其实,如若服务端和客户端相互通信,即客户端可以订阅可以发布,服务端可以订阅也可以发布,则可不区分服务端客户端,两边代码几乎一样。类似,两个客户端都在订阅同一主题,这时由第三个客户端发布这一主题的请求,前两个客户端同样可以接受该主题的内容,这时三个客户端的代码几乎一样,只是前两个是订阅,后一个是发布。
以上是自己纯碎学习所得,可能有很多bug,望后来人多多批评指正。