[net][at] add at_client_wait_connect

components/net/at/include/at.h

@@ -27,7 +27,7 @@
 
 #include <rtthread.h>
 
-#define AT_SW_VERSION                  "0.2.3"
+#define AT_SW_VERSION                  "0.2.4"
 
 #define DBG_ENABLE
 #define DBG_SECTION_NAME               "AT"
@@ -216,6 +216,9 @@ int at_req_parse_args(const char *req_args, const char *req_expr, ...);
 /* AT client initialize and start */
 int at_client_init(void);
 
+/* AT client wait for connection to external devices. */
+int at_client_wait_connect(rt_uint32_t timeout);
+
 /* AT client send commands to AT server and waiter response */
 int at_exec_cmd(at_response_t resp, const char *cmd_expr, ...);