IoT Platform:Connect to IoT Platform over HTTP

IoT Platform supports device connections over HTTP (HTTPS connection).

This Java example covers request parameter configuration and device-side signature calculation for connecting to IoT Platform over HTTP.

<dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>fastjson</artifactId>
  <version>1.2.83</version>
</dependency>

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.net.ssl.HttpsURLConnection;

import com.alibaba.fastjson.JSONObject;

/**
 * A device connects to Alibaba Cloud IoT Platform over HTTP. 
 * For more information about the protocol specifications, see "HTTP Protocol Specifications".
 * For more information about the data format, see "HTTPS Connection".
 */
public class IotHttpClient {

    // The region ID. China (Shanghai) is used as an example.
    private static String regionId = "cn-shanghai";

    // The encryption method. The Message Authentication Code (MAC) algorithm can be HmacMD5 or HmacSHA1. The algorithm must be the same as the value of signmethod.
    private static final String HMAC_ALGORITHM = "hmacsha1";

    // The token is valid for 7 days. Obtain a new token after it expires.
    private String token = null;

    /**
     * Initializes the HTTP client.
     * 
     * @param productKey The product key.
     * @param deviceName The device name.
     * @param deviceSecret The device secret.
     */
    public void conenct(String productKey, String deviceName, String deviceSecret) {
        try {
            // The registration URL.
            URL url = new URL("https://iot-as-http." + regionId + ".aliyuncs.com/auth");

            HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-type", "application/json");
            conn.setDoOutput(true);
            conn.setDoInput(true);

            // Get the output stream of the URLConnection object.
            PrintWriter out = new PrintWriter(conn.getOutputStream());
            // Send the request parameters.
            out.print(authBody(productKey, deviceName, deviceSecret));
            // Flush the buffer of the output stream.
            out.flush();

            // Get the input stream of the URLConnection object.
            BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            // Read the response from the URL.
            String result = "";
            String line = "";
            while ((line = in.readLine()) != null) {
                result += line;
            }
            System.out.println("----- auth result -----");
            System.out.println(result);

            // Close the input and output streams.
            in.close();
            out.close();
            conn.disconnect();

            // Get the token.
            JSONObject json = JSONObject.parseObject(result);
            if (json.getIntValue("code") == 0) {
                token = json.getJSONObject("info").getString("token");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * Sends a message.
     * 
     * @param topic The topic to which the message is sent.
     * @param payload The message content.
     */
    public void publish(String topic, byte[] payload) {
        try {
            // The registration URL.
            URL url = new URL("https://iot-as-http." + regionId + ".aliyuncs.com/topic" + topic);

            HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-type", "application/octet-stream");
            conn.setRequestProperty("password", token);
            conn.setDoOutput(true);
            conn.setDoInput(true);

            // Get the output stream of the URLConnection object.
            BufferedOutputStream out = new BufferedOutputStream(conn.getOutputStream());
            out.write(payload);
            out.flush();

            // Get the input stream of the URLConnection object.
            BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            // Read the response from the URL.
            String result = "";
            String line = "";
            while ((line = in.readLine()) != null) {
                result += line;
            }
            System.out.println("----- publish result -----");
            System.out.println(result);

            // Close the input and output streams.
            in.close();
            out.close();
            conn.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * Generates the authentication request content.
     * 
     * @param params The authentication parameters.
     * @return The authentication request message body.
     */
    private String authBody(String productKey, String deviceName, String deviceSecret) {

        // Construct the authentication request.
        JSONObject body = new JSONObject();
        body.put("productKey", productKey);
        body.put("deviceName", deviceName);
        body.put("clientId", productKey + "." + deviceName);
        body.put("timestamp", String.valueOf(System.currentTimeMillis()));
        body.put("signmethod", HMAC_ALGORITHM);
        body.put("version", "default");
        body.put("sign", sign(body, deviceSecret));

        System.out.println("----- auth body -----");
        System.out.println(body.toJSONString());

        return body.toJSONString();
    }

    /**
     * Signs the request on the device side.
     * 
     * @param params The parameters to be signed.
     * @param deviceSecret The device secret.
     * @return The signature as a hexadecimal string.
     */
    private String sign(JSONObject params, String deviceSecret) {

        // Sort the request parameters in alphabetical order.
        Set<String> keys = getSortedKeys(params);

        // Exclude sign, signmethod, and version.
        keys.remove("sign");
        keys.remove("signmethod");
        keys.remove("version");

        // Assemble the plaintext for signing.
        StringBuffer content = new StringBuffer();
        for (String key : keys) {
            content.append(key);
            content.append(params.getString(key));
        }

        // Calculate the signature.
        String sign = encrypt(content.toString(), deviceSecret);
        System.out.println("sign content=" + content);
        System.out.println("sign result=" + sign);

        return sign;
    }

    /**
     * Gets the sorted key set of a JSON object.
     * 
     * @param json The JSON object to be sorted.
     * @return The sorted key set.
     */
    private Set<String> getSortedKeys(JSONObject json) {
        SortedMap<String, String> map = new TreeMap<String, String>();
        for (String key : json.keySet()) {
            String value = json.getString(key);
            map.put(key, value);
        }
        return map.keySet();
    }

    /**
     * Encrypts data using HMAC_ALGORITHM.
     * 
     * @param content The plaintext.
     * @param secret The 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;
        }
    }

    /**
     * Converts a binary array to a hexadecimal string.
     * 
     * @param b The binary array.
     * @return The 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) {
        String productKey = "your-productKey";
        String deviceName = "your-deviceName";
        String deviceSecret = "your-deviceSecret";
        IotHttpClient client = new IotHttpClient();
        client.conenct(productKey, deviceName, deviceSecret);
        // The topic to which the message is sent. Customize the topic in the console. The device must have the permission to publish messages to the topic.
        String updateTopic = "/" + productKey + "/" + deviceName + "/user/update";
        client.publish(updateTopic, "hello http".getBytes(StandardCharsets.UTF_8));
        client.publish(updateTopic, new byte[] { 0x01, 0x02, 0x03 });
    }
}