MQTT 实战

摘要：协议版本版本介绍是一个用编写的客户端库用于开发在或其他兼容平台如上运行的应用程序提供了两个提供完全异步的通过注册的回调完成是的同步包装器例子这个就是官网提供的例子可以直接连上代理做测试的相关类介绍此类主要用于连接代理发布消息订阅消息断开连接

mqtt 协议版本: 3.1.1
eclipse paho client 版本: 1.2.0

Paho Java Client 是一个用Java编写的MQTT客户端库, 用于开发在JVM或其他Java兼容平台（如Android）上运行的应用程序.

Paho Java Client提供了两个API: MqttAsyncClient 提供完全异步的API, 通过注册的回调完成. MqttClient 是 MqttAsyncClient 的同步包装器.

        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();
        }

这个就是官网提供的例子, 可以直接连上代理做测试的.

此类主要用于连接代理、发布消息、订阅消息、断开连接.

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 {}

此类保存了客户端连接到代理时的一些参数.

public void setUserName(String userName) {}

public void setPassword(char[] password) {}

public void setConnectionTimeout(int connectionTimeout) {}

要发送的消息正文, 指定消息内容、Qos、Retained.

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