implemented downstream topic subscribe and receive

lib/AliyunIoTSDK/src/AliyunIoTSDK.cpp

@@ -148,7 +148,7 @@ int AliyunIoTSDK::mqttCheckConnect() {
     return mqttStatus;
 }
 
-void AliyunIoTSDK::begin(Client &espClient,
+int AliyunIoTSDK::begin(Client &espClient,
                          const char *_productKey,
                          const char *_deviceName,
                          const char *_deviceSecret,
@@ -189,7 +189,7 @@ void AliyunIoTSDK::begin(Client &espClient,
     client->setCallback(callback);
 #endif
 
-    mqttCheckConnect();
+    return mqttCheckConnect();
 }
 
 int AliyunIoTSDK::loop() {
@@ -236,6 +236,10 @@ void AliyunIoTSDK::sendCustomData(const char *topic, const uint8_t *data, int le
     Serial.println(d);
 }
 
+boolean AliyunIoTSDK::subscribe(const char* topic, int qos) {
+    return client->subscribe(topic, qos);
+}
+
 void AliyunIoTSDK::registerCustomCallback(MQTT_CALLBACK_SIGNATURE) {
     client->setCallback(callback);
 }

lib/AliyunIoTSDK/src/AliyunIoTSDK.h

@@ -64,11 +64,11 @@ public:
    * @param _deviceSecret : AliyunIoT device secret
    * @param _region : AliyunIoT region
    */
-  static void begin(Client &espClient,
-                    const char *_productKey,
-                    const char *_deviceName,
-                    const char *_deviceSecret,
-                    const char *_region);
+  static int begin(Client &espClient,
+                   const char *_productKey,
+                   const char *_deviceName,
+                   const char *_deviceSecret,
+                   const char *_region);
 
   /**
    * Send data
@@ -134,9 +134,18 @@ public:
    */
   static void sendCustomData(const char *topic, const uint8_t *data, int length);
 
+  /**
+   * Subscribe MQTT topic for Aliot
+   *
+   * @param topic : topic in string
+   * @param qos : MQTT qos param
+   * @return if succeeded
+   */
+  static boolean subscribe(const char* topic, int qos);
+
   /**
    * Register customized MQTT message callback
-   * 
+   *
    * @param callback : callback pointer
    */
   static void registerCustomCallback(MQTT_CALLBACK_SIGNATURE);