update mqtt client

update mqtt client

components/connectivity/mqttclient/common/random.h

@@ -2,17 +2,25 @@
  * @Author: jiejie
  * @Github: https://github.com/jiejieTop
  * @Date: 2020-01-09 19:59:19
- * @LastEditTime : 2020-01-10 08:52:45
+ * @LastEditTime: 2020-10-17 14:18:15
  * @Description: the code belongs to jiejie, please keep the author information and source code according to the license.
  */
 
 #ifndef _RANDOM_H_
 #define _RANDOM_H_
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define RANDOM_MAX 0x7FFFFFFF
 
 int random_number(void);
 int random_number_range(unsigned int min, unsigned int max);
 char *random_string(unsigned int len);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _RANDOM_H_ */