摘要：協議版本版本介紹是一個用編寫的客戶端庫用于開發在或其他兼容平臺如上運行的應用程序提供了兩個提供完全異步的通過注冊的回調完成是的同步包裝器例子這個就是官網提供的例子可以直接連上代理做測試的相關類介紹此類主要用于連接代理發布消息訂閱消息斷開連接

mqtt 協議版本: 3.1.1
eclipse paho client 版本: 1.2.0

Paho Java Client 是一個用Java編寫的MQTT客戶端庫, 用于開發在JVM或其他Java兼容平臺（如Android）上運行的應用程序.

Paho Java Client提供了兩個API: MqttAsyncClient 提供完全異步的API, 通過注冊的回調完成. MqttClient 是 MqttAsyncClient 的同步包裝器.

        String topic        = "MQTT Examples";
        String content      = "Message from MqttPublishSample";
        int qos             = 2;
        String broker       = "tcp://iot.eclipse.org:1883";
        String clientId     = "JavaSample";
        MemoryPersistence persistence = new MemoryPersistence();

        try {
            MqttClient sampleClient = new MqttClient(broker, clientId, persistence);
            MqttConnectOptions connOpts = new MqttConnectOptions();
            connOpts.setCleanSession(true);
            System.out.println("Connecting to broker: "+broker);
            sampleClient.connect(connOpts);
            System.out.println("Connected");
            System.out.println("Publishing message: "+content);
            MqttMessage message = new MqttMessage(content.getBytes());
            message.setQos(qos);
            sampleClient.publish(topic, message);
            System.out.println("Message published");
            sampleClient.disconnect();
            System.out.println("Disconnected");
            System.exit(0);
        } 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();
        }

這個就是官網提供的例子, 可以直接連上代理做測試的.

此類主要用于連接代理、發布消息、訂閱消息、斷開連接.

public void publish(String topic, byte[] payload,int qos, boolean retained) throws MqttException, MqttPersistenceException {}
public void publish(String topic, MqttMessage message) throws MqttException, MqttPersistenceException {}

public void subscribe(String topicFilter) throws MqttException {}
public void subscribe(String[] topicFilters) throws MqttException {}
public void subscribe(String topicFilter, int qos) throws MqttException {}
public void subscribe(String[] topicFilters, int[] qos) throws MqttException {}
public void subscribe(String topicFilter, IMqttMessageListener messageListener) throws MqttException {}
public void subscribe(String[] topicFilters, IMqttMessageListener[] messageListeners) throws MqttException {}
public void subscribe(String topicFilter, int qos, IMqttMessageListener messageListener) throws MqttException {}
public void subscribe(String[] topicFilters, int[] qos, IMqttMessageListener[] messageListeners) throws MqttException {}

public void connect() throws MqttSecurityException, MqttException {}
public void connect(MqttConnectOptions options) throws MqttSecurityException, MqttException {}

public void disconnect() throws MqttException {}
public void disconnect(long quiesceTimeout) throws MqttException {}

此類保存了客戶端連接到代理時的一些參數.

public void setUserName(String userName) {}

public void setPassword(char[] password) {}

public void setConnectionTimeout(int connectionTimeout) {}

要發送的消息正文, 指定消息內容、Qos、Retained.

public void setQos(int qos) {}
public void setPayload(byte[] payload) {}
public void setRetained(boolean retained) {}