编写和MQTT服务器通信的Android客户端程序（二）

客户端使用的API，开始我使用的是mqtt-client，使用过后发现问题百出，不能很好的满足要求，后来使用了官方推荐的Eclipse Paho，下面开始客户端代码的编写，为了方便测试这里有android和j2se两个工程：

1、新建android工程MQTTClient

2、MainActivity代码如下：

package ldw.mqttclient;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
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.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.KeyEvent;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

	private TextView resultTv;

	private String host = "tcp://127.0.0.1:1883";
	private String userName = "admin";
	private String passWord = "password";

	private Handler handler;

	private MqttClient client;

	private String myTopic = "test/topic";

	private MqttConnectOptions options;

	private ScheduledExecutorService scheduler;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		resultTv = (TextView) findViewById(R.id.result);

		init();

		handler = new Handler() {
			@Override
			public void handleMessage(Message msg) {
				super.handleMessage(msg);
				if(msg.what == 1) {
					Toast.makeText(MainActivity.this, (String) msg.obj,
							Toast.LENGTH_SHORT).show();
					System.out.println("-----------------------------");
				} else if(msg.what == 2) {
					Toast.makeText(MainActivity.this, "连接成功", Toast.LENGTH_SHORT).show();
					try {
						client.subscribe(myTopic, 1);
					} catch (Exception e) {
						e.printStackTrace();
					}
				} else if(msg.what == 3) {
					Toast.makeText(MainActivity.this, "连接失败，系统正在重连", Toast.LENGTH_SHORT).show();
				}
			}
		};

		startReconnect();

	}

	private void startReconnect() {
		scheduler = Executors.newSingleThreadScheduledExecutor();
		scheduler.scheduleAtFixedRate(new Runnable() {

			@Override
			public void run() {
				if(!client.isConnected()) {
					connect();
				}
			}
		}, 0 * 1000, 10 * 1000, TimeUnit.MILLISECONDS);
	}

	private void init() {
		try {
                       //host为主机名，test为clientid即连接MQTT的客户端ID，一般以客户端唯一标识符表示，MemoryPersistence设置clientid的保存形式，默认为以内存保存
			client = new MqttClient(host, "test",
					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 MqttCallback() {

				@Override
				public void connectionLost(Throwable cause) {
                                        //连接丢失后，一般在这里面进行重连
					System.out.println("connectionLost----------");
				}

				@Override
				public void deliveryComplete(IMqttDeliveryToken token) {
                                        //publish后会执行到这里
					System.out.println("deliveryComplete---------"
							+ token.isComplete());
				}

				@Override
				public void messageArrived(String topicName, MqttMessage message)
						throws Exception {
                                        //subscribe后得到的消息会执行到这里面
					System.out.println("messageArrived----------");
					Message msg = new Message();
					msg.what = 1;
					msg.obj = topicName+"---"+message.toString();
					handler.sendMessage(msg);
				}
			});
//			connect();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	private void connect() {
		new Thread(new Runnable() {

			@Override
			public void run() {
				try {
					client.connect(options);
					Message msg = new Message();
					msg.what = 2;
					handler.sendMessage(msg);
				} catch (Exception e) {
					e.printStackTrace();
					Message msg = new Message();
					msg.what = 3;
					handler.sendMessage(msg);
				}
			}
		}).start();
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if(client != null && keyCode == KeyEvent.KEYCODE_BACK) {
			try {
				client.disconnect();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return super.onKeyDown(keyCode, event);
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
		try {
			scheduler.shutdown();
			client.disconnect();
		} catch (MqttException e) {
			e.printStackTrace();
		}
	}
}

由于项目需要，我用到了心跳重连。根据这里的解释设置apollo.xml，主要有设置主机连接的地址。另外，options还有个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。

3、新建j2se工程MQTTServer

4、Server代码如下：

import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
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.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttTopic;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class Server extends JFrame {
	private static final long serialVersionUID = 1L;
	private JPanel panel;
	private JButton button;

	private MqttClient client;
	private String host = "tcp://127.0.0.1:1883";
//	private String host = "tcp://localhost:1883";
	private String userName = "test";
	private String passWord = "test";
	private MqttTopic topic;
	private MqttMessage message;

	private String myTopic = "test/topic";

	public Server() {

		try {
			client = new MqttClient(host, "Server",
					new MemoryPersistence());
			connect();
		} catch (Exception e) {
			e.printStackTrace();
		}

		Container container = this.getContentPane();
		panel = new JPanel();
		button = new JButton("发布话题");
		button.addActionListener(new ActionListener() {

			@Override
			public void actionPerformed(ActionEvent ae) {
				try {
					MqttDeliveryToken token = topic.publish(message);
					token.waitForCompletion();
					System.out.println(token.isComplete()+"========");
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
		panel.add(button);
		container.add(panel, "North");

	}

	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 MqttCallback() {

				@Override
				public void connectionLost(Throwable cause) {
					System.out.println("connectionLost-----------");
				}

				@Override
				public void deliveryComplete(IMqttDeliveryToken token) {
					System.out.println("deliveryComplete---------"+token.isComplete());
				}

				@Override
				public void messageArrived(String topic, MqttMessage arg1)
						throws Exception {
					System.out.println("messageArrived----------");

				}
			});

			topic = client.getTopic(myTopic);

			message = new MqttMessage();
			message.setQos(1);
			message.setRetained(true);
			System.out.println(message.isRetained()+"------ratained状态");
			message.setPayload("eeeeeaaaaaawwwwww---".getBytes());

			client.connect(options);
		} catch (Exception e) {
			e.printStackTrace();
		}

	}

	public static void main(String[] args) {
		Server s = new Server();
		s.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		s.setSize(600, 370);
		s.setLocationRelativeTo(null);
		s.setVisible(true);
	}
}

上面代码跟客户端的代码差不多，这里就不做解释了。

没什么好说的，MQTT就是这么简单，但开始在使用的时候要注意一些参数的设置来适应项目的需求。