diff --git a/components/net/at/at_socket/at_socket.c b/components/net/at/at_socket/at_socket.c
index f754ad52a703f113bf3015ee1beaaa3bf6378706..c21d0197175f026f4506a9dc109c5223304a1b8c 100644
--- a/components/net/at/at_socket/at_socket.c
+++ b/components/net/at/at_socket/at_socket.c
@@ -385,6 +385,9 @@ int at_closesocket(int socket)
         return -1;
     }
 
+    /* deal with TCP server actively disconnect */
+    rt_thread_delay(rt_tick_from_millisecond(100));
+    
     sock = at_get_socket(socket);
     if (sock == RT_NULL)
     {
@@ -401,10 +404,13 @@ int at_closesocket(int socket)
         if (at_dev_ops->at_closesocket(socket) != 0)
         {
             LOG_E("AT socket (%d) closesocket failed!", socket);
+            free_socket(sock);
+            return -1;
         }
     }
 
-    return free_socket(sock);
+    free_socket(sock); 
+    return 0;
 }
 
 int at_shutdown(int socket, int how)
@@ -427,10 +433,13 @@ int at_shutdown(int socket, int how)
         if (at_dev_ops->at_closesocket(socket) != 0)
         {
             LOG_E("AT socket (%d) shutdown failed!", socket);
+            free_socket(sock);
+            return -1;
         }
     }
 
-    return free_socket(sock);
+    free_socket(sock);
+    return 0;
 }
 
 int at_bind(int socket, const struct sockaddr *name, socklen_t namelen)
diff --git a/components/net/at/include/at.h b/components/net/at/include/at.h
index 6f4836fa214c079272c565409050140bdcafd23c..2601562019b6fc2ea3938cf864c160da75238ac2 100644
--- a/components/net/at/include/at.h
+++ b/components/net/at/include/at.h
@@ -31,7 +31,8 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
-#define AT_SW_VERSION                  "1.0.0"
+
+#define AT_SW_VERSION                  "1.0.1"
 #define AT_SW_VERSION_NUM              0x10000
 
 #define DBG_ENABLE
diff --git a/components/net/at/src/at_client.c b/components/net/at/src/at_client.c
index 9a515f4e8f4a3307d89decc0bb4f82f962d707e6..42a6f4b980972a9f6042ca37a8f463c5abde7adb 100644
--- a/components/net/at/src/at_client.c
+++ b/components/net/at/src/at_client.c
@@ -290,9 +290,14 @@ int at_obj_exec_cmd(at_client_t client, at_response_t resp, const char *cmd_expr
     rt_err_t result = RT_EOK;
     const char *cmd = RT_NULL;
 
-    RT_ASSERT(client);
     RT_ASSERT(cmd_expr);
 
+    if (client == RT_NULL)
+    {
+        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
+        return -RT_ERROR;
+    }
+
     rt_mutex_take(client->lock, RT_WAITING_FOREVER);
 
     client->resp_status = AT_RESP_OK;
@@ -348,8 +353,8 @@ int at_client_obj_wait_connect(at_client_t client, rt_uint32_t timeout)
 
     if (client == RT_NULL)
     {
-        LOG_E("Input AT Client is NULL, please create or get AT Client!");
-        return RT_NULL;
+        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
+        return -RT_ERROR;
     }
 
     resp = at_create_resp(16, 0, rt_tick_from_millisecond(500));
@@ -400,13 +405,19 @@ int at_client_obj_wait_connect(at_client_t client, rt_uint32_t timeout)
  * @param buf   send data buffer
  * @param size  send fixed data size
  *
- * @return send data size
+ * @return >0: send data size
+ *         =0: send failed
  */
 rt_size_t at_client_obj_send(at_client_t client, const char *buf, rt_size_t size)
 {
-    RT_ASSERT(client);
     RT_ASSERT(buf);
 
+    if (client == RT_NULL)
+    {
+        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
+        return 0;
+    }
+
 #ifdef AT_PRINT_RAW_CMD
     at_print_raw_cmd("send", buf, size);
 #endif
@@ -436,16 +447,22 @@ static char at_client_getchar(at_client_t client)
  *
  * @note this function can only be used in execution function of URC data
  *
- * @return success receive data size
+ * @return >0: receive data size
+ *         =0: receive failed
  */
 rt_size_t at_client_obj_recv(at_client_t client, char *buf, rt_size_t size)
 {
     rt_size_t read_idx = 0;
     char ch;
 
-    RT_ASSERT(client);
     RT_ASSERT(buf);
 
+    if (client == RT_NULL)
+    {
+        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
+        return 0;
+    }
+
     while (1)
     {
         if (read_idx < size)
@@ -475,7 +492,11 @@ rt_size_t at_client_obj_recv(at_client_t client, char *buf, rt_size_t size)
  */
 void at_obj_set_end_sign(at_client_t client, char ch)
 {
-    RT_ASSERT(client);
+    if (client == RT_NULL)
+    {
+        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
+        return;
+    }
 
     client->end_sign = ch;
 }
@@ -491,6 +512,12 @@ void at_obj_set_urc_table(at_client_t client, const struct at_urc *urc_table, rt
 {
     rt_size_t idx;
 
+    if (client == RT_NULL)
+    {
+        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
+        return;
+    }
+
     for (idx = 0; idx < table_sz; idx++)
     {
         RT_ASSERT(urc_table[idx].cmd_prefix);