This article describes how to dynamically register the devices that use the MQTT protocol and obtain the DeviceSecrets. The DeviceSecrets are required for authentication when you connect the devices to IoT Platform. In this example, the sample Java code is used for pre-registration unique-certificate-per-product authentication.

Prerequisites

The following steps that are specified in the Unique-certificate-per-product authentication topic are performed:

  1. Create a product.
  2. Enable dynamic registration.
  3. Add a device.
  4. Burn the device certificate to the device.

Background information

IoT Platform supports multiple authentication methods for devices. For more information, see Authenticate a device.

You can establish MQTT connections to perform pre-registration unique-certificate-per-product authentication or preregistration-free unique-certificate-per-product authentication. For more information about the procedure and parameters of MQTT-based dynamic registration, see MQTT-based dynamic registration.

Procedure

  1. Open IntelliJ IDEA and create a Maven project. In this example, the MQTT dynamic registration project is created.
  2. In the pom.xml file, add the following Maven dependencies and click Load Maven Changes to download the packages.
    <dependency>
      <groupId>org.eclipse.paho</groupId>
      <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
      <version>1.2.1</version>
    </dependency>
    
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.61</version>
    </dependency>
  3. Go to the \MQTT dynamic registration \src\main\java directory and create a Java class. In this example, the DynamicRegisterByMqtt class is created. Enter the following code.
    Note
    • If the device is not activated, dynamic registration can be performed multiple times. In this case, only the latest DeviceSecret is valid. Make sure that the latest DeviceSecret is persisted on the device.
    • If the device is activated, you must call the ResetThing operation to reset the device status in IoT Platform to inactive. Then, you can dynamically register the device.
    /*   
     * Copyright © 2019 Alibaba. All rights reserved.
     */
    package com.aliyun.iot.demo;
    
    import java.nio.charset.StandardCharsets;
    import java.util.Random;
    import java.util.Set;
    import java.util.SortedMap;
    import java.util.TreeMap;
    
    import javax.crypto.Mac;
    import javax.crypto.spec.SecretKeySpec;
    
    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 com.alibaba.fastjson.JSONObject;
    
    /**
     * Perform dynamic registration for a device. 
     */
    public class DynamicRegisterByMqtt {
    
        // The ID of the region where your product resides.
        private static String regionId = "cn-shanghai";
    
        // Specify an encryption algorithm. Valid values: hmacmd5, hmacsha1, and hmacsha256. The value that you specify must be the same as the value of the signmethod parameter.
        private static final String HMAC_ALGORITHM = "hmacsha1";
    
        // The topic that receives device certificates from IoT Platform. Use the topic without any changes. You do not need to create or subscribe to the topic.
        private static final String REGISTER_TOPIC = "/ext/register";
    
        /**
         * Dynamic registration.
         * 
         * @ param productKey: the ProductKey of the product.
         * @param productSecret: the ProductSecret of the device.
         * @param deviceName: the DeviceName of the device.
         * @throws Exception
         */
        public void register(String productKey, String productSecret, String deviceName) throws Exception {
    
            // The endpoint of the authentication service. You must use the Transport Layer Security (TLS) protocol.
            String broker = "ssl://" + productKey + ".iot-as-mqtt." + regionId + ".aliyuncs.com:1883";
    
            // The client ID. We recommend that you use the MAC address or SN of the device. The client ID can be a maximum of 64 characters in length.
            String clientId = productKey + "." + deviceName;
    
            // Obtain a random value.
            Random r = new Random();
            int random = r.nextInt(1000000);
    
            // The value of the securemode parameter is 2 and cannot be changed. The value 2 indicates that TLS is applied. The signmethod parameter specifies an encryption algorithm.
            String clientOpts = "|securemode=2,authType=register,signmethod=" + HMAC_ALGORITHM + ",random=" + random + "|";
    
            // The ID of the MQTT client.
            String mqttClientId = clientId + clientOpts;
    
            // The usename of the MQTT client.
            String mqttUsername = deviceName + "&" + productKey;
    
            // The signature that the MQTT client uses to connect to the endpoint.
            JSONObject params = new JSONObject();
            params.put("productKey", productKey);
            params.put("deviceName", deviceName);
            params.put("random", random);
            String mqttPassword = sign(params, productSecret);
    
            // Send an MQTT CONNECT message for dynamic registration.
            connect(broker, mqttClientId, mqttUsername, mqttPassword);
        }
    
        /**
         * Send an MQTT CONNECT message for dynamic registration.
         * 
         * @param serverURL: the endpoint for dynamic registration.
         * @param clientId: the ID of the client.
         * @param username: the username of the MQTT client.
         * @param password: the password of the MQTT client.
         */
        @SuppressWarnings("resource")
        private void connect(String serverURL, String clientId, String username, String password) {
            try {
                MemoryPersistence persistence = new MemoryPersistence();
                MqttClient sampleClient = new MqttClient(serverURL, clientId, persistence);
                MqttConnectOptions connOpts = new MqttConnectOptions();
                connOpts.setMqttVersion(4);// MQTT 3.1.1
                connOpts.setUserName(username);// The username.
                connOpts.setPassword(password.toCharArray());// The password.
                connOpts.setAutomaticReconnect(false); // Disable the automatic reconnection feature based on MQTT rules that are set for dynamic registration.
                System.out.println("----- register params -----");
                System.out.print("server=" + serverURL + ",clientId=" + clientId);
                System.out.println(",username=" + username + ",password=" + password);
                sampleClient.setCallback(new MqttCallback() {
                    @Override
                    public void messageArrived(String topic, MqttMessage message) throws Exception {
                        // Print out only the response of dynamic registration.
                        if (REGISTER_TOPIC.equals(topic)) {
                            String payload = new String(message.getPayload(), StandardCharsets.UTF_8);
                            System.out.println("----- register result -----");
                            System.out.println(payload);
                            sampleClient.disconnect();
                        }
                    }
    
                    @Override
                    public void deliveryComplete(IMqttDeliveryToken token) {
                    }
    
                    @Override
                    public void connectionLost(Throwable cause) {
                    }
                });
                sampleClient.connect(connOpts);
            } catch (MqttException e) {
                System.out.print("register failed: clientId=" + clientId);
                System.out.println(",username=" + username + ",password=" + password);
                System.out.println("reason " + e.getReasonCode());
                System.out.println("msg " + e.getMessage());
                System.out.println("loc " + e.getLocalizedMessage());
                System.out.println("cause " + e.getCause());
                System.out.println("excep " + e);
                e.printStackTrace();
            }
        }
    
        /**
         * Generate a signature for dynamic registration.
         * 
         * @param params: the required parameters that you can use to generate a signature.
         * @param productSecret: the ProductSecret of the device.
         * @return: a hexadecimal signature string.
         */
        private String sign(JSONObject params, String productSecret) {
    
            // Sort request parameters in alphabetical order.
            Set<String> keys = getSortedKeys(params);
    
            // Remove the sign and signMethod parameters.
            keys.remove("sign");
            keys.remove("signMethod");
    
            // Obtain the plaintext of the signature.
            StringBuffer content = new StringBuffer();
            for (String key : keys) {
                content.append(key);
                content.append(params.getString(key));
            }
    
            // Generate a signature.
            String sign = encrypt(content.toString(), productSecret);
            System.out.println("sign content=" + content);
            System.out.println("sign result=" + sign);
    
            return sign;
        }
    
        /**
         * Convert a JSON object to a set of key-value pairs.
         *
         * @param json: the JSON object to be converted.
         * @return: a set of key-value pairs that are converted from the JSON object.
         */
        private Set<String> getSortedKeys(JSONObject json) {
            SortedMap<String, String> map = new TreeMap<String, String>();
            for (String key : json.keySet()) {
                String vlaue = json.getString(key);
                map.put(key, vlaue);
            }
            return map.keySet();
        }
    
        /**
         * Specify an encryption algorithm for the HMAC_ALGORITHM parameter.
         * 
         * @param content: the plaintext.
         * @param secret: the encryption key.
         * @return: the ciphertext.
         */
        private String encrypt(String content, String secret) {
            try {
                byte[] text = content.getBytes(StandardCharsets.UTF_8);
                byte[] key = secret.getBytes(StandardCharsets.UTF_8);
                SecretKeySpec secretKey = new SecretKeySpec(key, HMAC_ALGORITHM);
                Mac mac = Mac.getInstance(secretKey.getAlgorithm());
                mac.init(secretKey);
                return byte2hex(mac.doFinal(text));
            } catch (Exception e) {
                e.printStackTrace();
                return null;
            }
        }
    
        /**
         * Convert a binary array to a hexadecimal string.
         * 
         * @param b: the binary array.
         * @return: a hexadecimal string.
         */
        private String byte2hex(byte[] b) {
            StringBuffer sb = new StringBuffer();
            for (int n = 0; b != null && n < b.length; n++) {
                String stmp = Integer.toHexString(b[n] & 0XFF);
                if (stmp.length() == 1) {
                    sb.append('0');
                }
                sb.append(stmp);
            }
            return sb.toString().toUpperCase();
        }
    
        public static void main(String[] args) throws Exception {
    
            String productKey = "a1IoK******";
            String productSecret = "6vEu5Qlj5S******";
            String deviceName = "OvenDevice01";
    
            // Perform dynamic registration.
            DynamicRegisterByMqtt client = new DynamicRegisterByMqtt();
            client.register(productKey, productSecret, deviceName);
    
            // After dynamic registration is successful, persist the DeviceSecret on premises.
        }
    }
    Parameter Example Description
    regionId cn-shanghai The ID of the region where IoT Platform runs.

    You can view the region in the upper-left corner of the IoT Platform console. For more information about the format of the RegionId parameter, see Regions and zones.

    productKey a1IoK****** The ProductKey that is burned to the device. You can log on to the IoT Platform console and view the ProductKey on the Product Details page.
    productSecret 6vEu5Qlj5S****** The ProductSecret that is burned to the device. You can log on to the IoT Platform console and view the ProductSecret on the Product Details page.
    deviceName OvenDevice01 The name of the device.

    IoT Platform authenticates the DeviceName when a device initiates an activation request. We recommend that you use an identifier that can be obtained from the device as the DeviceName. The identifier can be the MAC address, IMEI, or SN of the device.

  4. Run the DynamicRegisterByMqtt.java file so that the device can send an authentication request to IoT Platform. The DeviceName, ProductKey, and ProductSecret are included in the request.

    The following figure shows the result. After the device passes the authentication, the device receives a DeviceSecret that is issued by IoT Platform. In this example, the DeviceSecret is 8d1f0cdab49dd229cf3b75**********.

    Result

What to do next

After the device obtains the device certificate (ProductKey, DeviceName, and DeviceSecret), you can use the MQTT client to connect the device with IoT Platform for data communication.

For more information, see Use the Paho MQTT Java client.