首先物联网协议mqtt协议是基于tcp/ip协议的，使用了官方的mqttclient框架

/*
*初始化mqttclient
*/
private void init() {
        try {
            //MQTT的连接设置
            options = new MqttConnectOptions();
            //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(new Ip().host, username,
                    new MemoryPersistence());
            //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(false);
//options.setWill(myTopic,null,2,false);

            //设置连接的用户名
            options.setUserName(login_token);
            //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(60);
            //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 {
                    byte[] message1 = message.getPayload();
                    //  subscribe后得到的消息会执行到这里面
                    System.out.println("messageArrived----------" + message1[0] + Arrays.toString(message1));
                    System.out.println(message1[0] == 5);
                    String id = new String(subBytes(message1, 1, 16), "UTF-8");

                    System.out.print("mqtt收到的id" + id);
                    DeviceList device = getBookById(id);
                    System.out.print("device" + device.getName());
                    String name = device.getName();
                    String gName = device.getgName();
                    String type = device.getType();
                    System.out.print("名字为" + name + gName);
                    /**
                    * 使用handler发送matt接收的消息，格式为二进制数据
                    * */

                    Message msg = new Message();
                    msg.what = 1;
                    if (message1[0] == 1) {
//                        msg.obj = name + "设备心跳";
//                        handler.sendMessage(msg);
                        return;
                    }
                    if (message1[0] == 2) {
                        msg.obj = gName + "" + name + "报警";
                        msg.arg1 = Integer.parseInt(type);
                        handler.sendMessage(msg);
                        return;
                    }
                    if (message1[0] == 3) {
                        msg.obj = gName + "" + name + "上线";
                        handler.sendMessage(msg);
                        return;
                    }
                    if (message1[0] == 4) {
                        msg.obj = gName + "" + name + "离线";
                        handler.sendMessage(msg);
                        return;
                    }
                    if (message1[0] == 5) {
                        if (message1[17] == 0) {
                            msg.obj = gName + "" + name + "关门";
                        } else {
                            msg.obj = gName + "" + name + "开门";
                        }


                        handler.sendMessage(msg);
                        return;
                    }
                    if (message1[0] == 20 && message1[17] > 0 && message1[17] < 20) {

                        msg.obj = name + "电池电量:  " + message1[17] + "%";
                        handler.sendMessage(msg);
                        System.out.println("电池:" + name + "电池电量:  " + message1[17] + "%");
                        return;
                    }
                    if (message1[17] > 0) {
                        SharedPreferences sp = getActivity().getSharedPreferences(id, getActivity().MODE_PRIVATE);
                        // 获得sp的编辑器
                        SharedPreferences.Editor ed = sp.edit();
                        // 以键值对的显示将用户名和密码保存到sp中
                        ed.putString("battery", String.valueOf(message1[17]));
                        // 提交用户名和密码
                        ed.commit();
                    }
                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public byte[] subBytes(byte[] src, int begin, int count) {
        byte[] bs = new byte[count];
        System.arraycopy(src, begin, bs, 0, count);
        return bs;
    }

    //根据id拿到属性为id的Book对象。
    public static DeviceList getBookById(String id) {
        DeviceList book = new DeviceList();
        book.setId(id);//设置传入的id值
        //books.indexOf()根据id比较对象是否相等
        return deviceList1.get(deviceList1.indexOf(book));
        //返回关联id的Book对象。
    }

    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();
    }

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

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

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

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