add license information

tcpclient/tcpclient_sample.c

@@ -1,3 +1,12 @@
+/* 
+ * Copyright (c) 2006-2018, RT-Thread Development Team 
+ * 
+ * SPDX-License-Identifier: Apache-2.0 
+ * 
+ * Change Logs: 
+ * Date             Author      Notes
+ * 
+ */
 /*
  * 程序清单：tcp 客户端
  *

tcpclient_select/tcpclient_select_sample.c

@@ -1,3 +1,12 @@
+/* 
+ * Copyright (c) 2006-2018, RT-Thread Development Team 
+ * 
+ * SPDX-License-Identifier: Apache-2.0 
+ * 
+ * Change Logs: 
+ * Date             Author      Notes
+ * 
+ */
 /*
  * 程序清单：tcp 客户端
  *

tcpserver/tcpserver_sample.c

@@ -1,3 +1,12 @@
+/* 
+ * Copyright (c) 2006-2018, RT-Thread Development Team 
+ * 
+ * SPDX-License-Identifier: Apache-2.0 
+ * 
+ * Change Logs: 
+ * Date             Author      Notes
+ * 
+ */
 /*
 * 程序清单：tcp 服务端
  *

udpclient/udpclient_sample.c

@@ -1,3 +1,12 @@
+/* 
+ * Copyright (c) 2006-2018, RT-Thread Development Team 
+ * 
+ * SPDX-License-Identifier: Apache-2.0 
+ * 
+ * Change Logs: 
+ * Date             Author      Notes
+ * 
+ */
 /*
  * 程序清单：udp 客户端
  *

udpserver/udpserver_sample.c

@@ -1,3 +1,12 @@
+/* 
+ * Copyright (c) 2006-2018, RT-Thread Development Team 
+ * 
+ * SPDX-License-Identifier: Apache-2.0 
+ * 
+ * Change Logs: 
+ * Date             Author      Notes
+ * 
+ */
 /*
 * 程序清单：udp 服务端
  *