Connect the gateway device to IoT Platform

    private static String regionId = "cn-shanghai";
    private static final String TAG = "TOPO";

    // The information about the gateway device.
    private static String GWproductKey = "a1BxptK***";
    private static String GWdeviceName = "XMtrv3yvftEHAzrTfX1U";
    private static String GWdeviceSecret = "19xJNybifnmgcK057vYhazYK4b64****";


    public static void main(String[] args) {
        /**
         * The information about the MQTT connection.
         */
        DeviceTopoManager manager = new DeviceTopoManager();

        /**
         * The Java HTTP client of this device supports TSLv1.2.
         */
        System.setProperty("https.protocols", "TLSv2");

        manager.init();
    }

public void init() {
        LinkKitInitParams params = new LinkKitInitParams();
        /**
         * Specify the parameters for MQTT initialization.
         */
        IoTMqttClientConfig config = new IoTMqttClientConfig();
        config.productKey = GWproductKey;
        config.deviceName = GWdeviceName;
        config.deviceSecret = GWdeviceSecret;
        config.channelHost = GWproductKey + ".iot-as-mqtt." + regionId + ".aliyuncs.com:1883";
        /**
         * Specify whether to receive offline messages.
         * The cleanSession field that corresponds to the MQTT connection.
         */
        config.receiveOfflineMsg = false;
        params.mqttClientConfig = config;
        ALog.setLevel(LEVEL_DEBUG);
        ALog.i(TAG, "mqtt connetcion info=" + params);

        /**
         * Configure the initialization and pass in the certificate information about the device.
         */
        DeviceInfo deviceInfo = new DeviceInfo();
        deviceInfo.productKey = GWproductKey;
        deviceInfo.deviceName = GWdeviceName;
        deviceInfo.deviceSecret = GWdeviceSecret;
        params.deviceInfo = deviceInfo;

        /**Establish a connection. **/
        LinkKit.getInstance().init(params, new ILinkKitConnectListener() {
            public void onError(AError aError) {
                ALog.e(TAG, "Init Error error=" + aError);
            }

            public void onInitDone(InitResult initResult) {
                ALog.i(TAG, "onInitDone result=" + initResult);


                // Obtain the topological relationships of the gateway and check whether a topological relationship exists between the gateway and the sub-device.
                // If a topological relationship exists between the gateway and the sub-device, the gateway connects the sub-device to IoT Platform.
                getGWDeviceTopo();

                // Dynamically register the sub-device to obtain a DeviceSecret for the sub-device. If the gateway has obtained the certificate of the sub-device, skip this step.
                // When you register the sub-device, set the deviceName parameter to the serial number or MAC address of the sub-device.
                gatewaySubDevicRegister();

                //Specify the information about the sub-device for which you want to add a topological relationship.
                gatewayAddSubDevice();


            }
        });
    }