服務端代碼:
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: 服務器向多個客戶端推送主題,即不同客戶端可向服務器訂閱相同主題
* @author
* 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設置clientid的保存形式,默認爲以內存保存
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());
// 設置超時時間
options.setConnectionTimeout(10);
// 設置會話心跳時間
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("給客戶端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("給客戶端125推送的信息".getBytes());
server.publish(server.topic125 , server.message);
System.out.println(server.message.isRetained() + "------ratained狀態");
}
}
客戶端代碼:
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爲主機名,clientid即連接MQTT的客戶端ID,一般以唯一標識符表示,MemoryPersistence設置clientid的保存形式,默認爲以內存保存
client = new MqttClient(HOST, clientid, new MemoryPersistence());
// MQTT的連接設置
options = new MqttConnectOptions();
// 設置是否清空session,這裏如果設置爲false表示服務器會保留客戶端的連接記錄,這裏設置爲true表示每次連接到服務器都以新的身份連接
options.setCleanSession(true);
// 設置連接的用戶名
options.setUserName(userName);
// 設置連接的密碼
options.setPassword(passWord.toCharArray());
// 設置超時時間 單位爲秒
options.setConnectionTimeout(10);
// 設置會話心跳時間 單位爲秒 服務器會每隔1.5*20秒的時間向客戶端發送個消息判斷客戶端是否在線,但這個方法並沒有重連的機制
options.setKeepAliveInterval(20);
// 設置回調
client.setCallback(new PushCallback());
MqttTopic topic = client.getTopic(TOPIC);
//setWill方法,如果項目中需要知道客戶端是否掉線可以調用該方法。設置最終端口的通知消息
options.setWill(topic, "close".getBytes(), 2, true);
client.connect(options);
//訂閱消息
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訂閱回調類:
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttMessage;
/**
* 發佈消息的回調類
*
* 必須實現MqttCallback的接口並實現對應的相關接口方法CallBack 類將實現 MqttCallBack。
* 每個客戶機標識都需要一個回調實例。在此示例中,構造函數傳遞客戶機標識以另存爲實例數據。
* 在回調中,將它用來標識已經啓動了該回調的哪個實例。
* 必須在回調類中實現三個方法:
*
* public void messageArrived(MqttTopic topic, MqttMessage message)接收已經預訂的發佈。
*
* public void connectionLost(Throwable cause)在斷開連接時調用。
*
* public void deliveryComplete(MqttDeliveryToken token))
* 接收到已經發布的 QoS 1 或 QoS 2 消息的傳遞令牌時調用。
* 由 MqttClient.connect 激活此回調。
*
*/
public class PushCallback implements MqttCallback {
public void connectionLost(Throwable cause) {
// 連接丟失後,一般在這裏面進行重連
System.out.println("連接斷開,可以做重連");
}
public void deliveryComplete(IMqttDeliveryToken token) {
System.out.println("deliveryComplete---------" + token.isComplete());
}
public void messageArrived(String topic, MqttMessage message) throws Exception {
// subscribe後得到的消息會執行到這裏面
System.out.println("接收消息主題 : " + topic);
System.out.println("接收消息Qos : " + message.getQos());
System.out.println("接收消息內容 : " + new String(message.getPayload()));
}
}
運行服務端代碼,可看到服務器會給客戶端124/125各推送一條消息,
在運行124客戶端代碼,可看到124客戶端接收的信息:
然後把客戶端代碼的Topic改爲TOPIC = "toclient/125";clientid = "client125";再運行該段代碼,可看到125客戶端接收的信息:
多個客戶端訂閱同一主題,其clientid必不相同。客戶端124/125訂閱各自主題的內容,但是不同時間啓動,都在啓動後接收到各自信息,這體現出了服務器的推送功能。同樣的,發送的主題信息,可以在服務器的topic可以看到,訪問路徑是:http://127.0.0.1:61680/
其實,如若服務端和客戶端相互通信,即客戶端可以訂閱可以發佈,服務端可以訂閱也可以發佈,則可不區分服務端客戶端,兩邊代碼幾乎一樣。類似,兩個客戶端都在訂閱同一主題,這時由第三個客戶端發佈這一主題的請求,前兩個客戶端同樣可以接受該主題的內容,這時三個客戶端的代碼幾乎一樣,只是前兩個是訂閱,後一個是發佈。
原文地址:http://www.cnblogs.com/chenrunlin/p/5109028.html