MQTT 实战

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

eclipse paho client 介绍

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.

例子

        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.

相关类介绍

MqttClient

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 {}

MqttConnectOptions

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) {}

MqttMessage

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) {}