6 files changed, 300 insertions, 245 deletions
diff --git a/examples/file/readwrite.c b/examples/file/readwrite.c
index 8dc29837ef..17d173c353 100644
--- a/examples/file/readwrite.c
+++ b/examples/file/readwrite.c
@@ -1,30 +1,24 @@
 /*
- * File      : readwrite.c
- * This file is part of RT-TestCase in RT-Thread RTOS
- * COPYRIGHT (C) 2010, RT-Thread Development Team
+ * 代码清单：文件读写例子
  *
- * The license and distribution terms for this file may be
- * found in the file LICENSE in this distribution or at
- * http://www.rt-thread.org/license/LICENSE
- *
- * Change Logs:
- * Date           Author       Notes
- * 2010-02-10     Bernard      first version
+ * 这个例子演示了如何读写一个文件，特别是写的时候应该如何操作。
  */
+
 #include <rtthread.h>
-#include <dfs_posix.h>
+#include <dfs_posix.h> /* 当需要使用文件操作时，需要包含这个头文件 */
 
 #define TEST_FN		"/test.dat"
 
+/* 测试用的数据和缓冲 */
 static char test_data[120], buffer[120];
 
-/* �ļ���д���� */
+/* 文件读写测试 */
 void readwrite(const char* filename)
 {
 	int fd;
 	int index, length;
 
-	/* ֻд & ���� �� */
+	/* 只写 & 创建 打开 */
 	fd = open(TEST_FN, O_WRONLY | O_CREAT | O_TRUNC, 0);
 	if (fd < 0)
 	{
@@ -32,13 +26,13 @@ void readwrite(const char* filename)
 		return;
 	}
 
-	/* ׼��д������ */
+	/* 准备写入数据 */
 	for (index = 0; index < sizeof(test_data); index ++)
 	{
 		test_data[index] = index + 27;
 	}
 
-	/* д������ */
+	/* 写入数据 */
 	length = write(fd, test_data, sizeof(test_data));
 	if (length != sizeof(test_data))
 	{
@@ -47,10 +41,10 @@ void readwrite(const char* filename)
 		return;
 	}
 
-	/* �ر��ļ� */
+	/* 关闭文件 */
 	close(fd);
 
-	/* ֻд����ĩβ���Ӵ� */
+	/* 只写并在末尾添加打开 */
 	fd = open(TEST_FN, O_WRONLY | O_CREAT | O_APPEND, 0);
 	if (fd < 0)
 	{
@@ -65,10 +59,10 @@ void readwrite(const char* filename)
 		close(fd);
 		return;
 	}
-	/* �ر��ļ� */
+	/* 关闭文件 */
 	close(fd);
 
-	/* ֻ���򿪽�������У�� */
+	/* 只读打开进行数据校验 */
 	fd = open(TEST_FN, O_RDONLY, 0);
 	if (fd < 0)
 	{
@@ -76,6 +70,7 @@ void readwrite(const char* filename)
 		return;
 	}
 
+	/* 读取数据(应该为第一次写入的数据) */
 	length = read(fd, buffer, sizeof(buffer));
 	if (length != sizeof(buffer))
 	{
@@ -83,6 +78,8 @@ void readwrite(const char* filename)
 		close(fd);
 		return;
 	}
+
+	/* 检查数据是否正确 */
 	for (index = 0; index < sizeof(test_data); index ++)
 	{
 		if (test_data[index] != buffer[index])
@@ -93,6 +90,7 @@ void readwrite(const char* filename)
 		}
 	}
 
+	/* 读取数据(应该为第二次写入的数据) */
 	length = read(fd, buffer, sizeof(buffer));
 	if (length != sizeof(buffer))
 	{
@@ -100,6 +98,8 @@ void readwrite(const char* filename)
 		close(fd);
 		return;
 	}
+
+	/* 检查数据是否正确 */
 	for (index = 0; index < sizeof(test_data); index ++)
 	{
 		if (test_data[index] != buffer[index])
@@ -109,13 +109,15 @@ void readwrite(const char* filename)
 			return;
 		}
 	}
-	/* ���������ϣ��ر��ļ� */
+
+	/* 检查数据完毕，关闭文件 */
 	close(fd);
-	/* ��ӡ��� */
+	/* 打印结果 */
 	rt_kprintf("read/write done.\n");
 }
 
 #ifdef RT_USING_FINSH
 #include <finsh.h>
+/* 输出函数到finsh shell命令行中 */
 FINSH_FUNCTION_EXPORT(readwrite, perform file read and write test);
 #endif
diff --git a/examples/kernel/event_simple.c b/examples/kernel/event_simple.c
index c98d99a2ab..069433b904 100644
--- a/examples/kernel/event_simple.c
+++ b/examples/kernel/event_simple.c
@@ -14,9 +14,11 @@ static rt_thread_t tid1 = RT_NULL;
 static rt_thread_t tid2 = RT_NULL;
 static rt_thread_t tid3 = RT_NULL;
 
-struct rt_event event;
+/* 事件控制块 */
+static struct rt_event event;
 
-void thread1_entry(void *param)
+/* 线程1入口函数 */
+static void thread1_entry(void *param)
 {
 	rt_uint32_t e;
 
@@ -31,7 +33,7 @@ void thread1_entry(void *param)
 		}
 
 		rt_kprintf("thread1: delay 1s to prepare second event\n");
-		rt_thread_delay(100);
+		rt_thread_delay(10);
 
 		/* receive second event */
 		if (rt_event_recv(&event, ((1 << 3) | (1 << 5)),
@@ -41,34 +43,37 @@ void thread1_entry(void *param)
 			rt_kprintf("thread1: OR recv event 0x%x\n", e);
 		}
 
-		rt_thread_delay(50);
+		rt_thread_delay(5);
 	}
 }
 
-void thread2_entry(void *param)
+/* 线程2入口函数 */
+static void thread2_entry(void *param)
 {
 	while (1)
 	{
 		rt_kprintf("thread2: send event1\n");
 		rt_event_send(&event, (1 << 3));
 
-		rt_thread_delay(100);
+		rt_thread_delay(10);
 	}
 }
 
-void thread3_entry(void *param)
+/* 线程3入口函数 */
+static void thread3_entry(void *param)
 {
 	while (1)
 	{
 		rt_kprintf("thread3: send event2\n");
 		rt_event_send(&event, (1 << 5));
 
-		rt_thread_delay(200);
+		rt_thread_delay(20);
 	}
 }
 
 int event_simple_init()
 {
+	/* 初始化事件对象 */
 	rt_event_init(&event, "event", RT_IPC_FLAG_FIFO);
 
 	/* 创建线程1 */
@@ -115,6 +120,9 @@ static void _tc_cleanup()
 	if (tid3 != RT_NULL && tid3->stat != RT_THREAD_CLOSE)
 		rt_thread_delete(tid3);
 
+	/* 执行事件对象脱离 */
+	rt_event_detach(&event);
+
 	/* 调度器解锁 */
 	rt_exit_critical();
 
diff --git a/examples/network/tcpclient.c b/examples/network/tcpclient.c
index 559a108d46..73f028655a 100644
--- a/examples/network/tcpclient.c
+++ b/examples/network/tcpclient.c
@@ -1,81 +1,95 @@
 #include <rtthread.h>
-#include <lwip/netdb.h>
-#include <lwip/sockets.h>
+#include <lwip/netdb.h> /* 为了解析主机名，需要包含netdb.h头文件 */
+#include <lwip/sockets.h> /* 使用BSD socket，需要包含sockets.h头文件 */
 
-static const char send_data[] = "This is TCP Client from RT-Thread.";
+static const char send_data[] = "This is TCP Client from RT-Thread."; /* 发送用到的数据 */
 void tcpclient(const char* url, int port)
 {
-	char *recv_data;
-	struct hostent *host;
-	int sock, bytes_received;
-	struct sockaddr_in server_addr;
+   char *recv_data;
+   struct hostent *host;
+   int sock, bytes_received;
+   struct sockaddr_in server_addr;
 
-	host = gethostbyname(url);
+   /* 通过函数入口参数url获得host地址（如果是域名，会做域名解析） */
+   host = gethostbyname(url);
 
-    recv_data = rt_malloc(1024);
-    if (recv_data == RT_NULL)
-    {
-        rt_kprintf("No memory\n");
-        return;
-    }
+   /* 分配用于存放接收数据的缓冲 */
+   recv_data = rt_malloc(1024);
+   if (recv_data == RT_NULL)
+   {
+       rt_kprintf("No memory\n");
+       return;
+   }
 
-	if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
-	{
-		rt_kprintf("Socket error\n");
+   /* 创建一个socket，类型是SOCKET_STREAM，TCP类型 */
+   if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
+   {
+       /* 创建socket失败 */
+       rt_kprintf("Socket error\n");
 
-        /* release recv buffer */
-        rt_free(recv_data);
-		return;
-	}
+       /* 释放接收缓冲 */
+       rt_free(recv_data);
+       return;
+   }
 
-	server_addr.sin_family = AF_INET;
-	server_addr.sin_port = htons(port);
-	server_addr.sin_addr = *((struct in_addr *)host->h_addr);
-	rt_memset(&(server_addr.sin_zero), 0, sizeof(server_addr.sin_zero));
+   /* 初始化预连接的服务端地址 */
+   server_addr.sin_family = AF_INET;
+   server_addr.sin_port = htons(port);
+   server_addr.sin_addr = *((struct in_addr *)host->h_addr);
+   rt_memset(&(server_addr.sin_zero), 0, sizeof(server_addr.sin_zero));
 
-	if (connect(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
-	{
-		rt_kprintf("Connect error\n");
+   /* 连接到服务端 */
+   if (connect(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
+   {
+       /* 连接失败 */
+       rt_kprintf("Connect error\n");
 
-        /* release recv buffer */
-        rt_free(recv_data);
-		return;
-	}
+       /*释放接收缓冲 */
+       rt_free(recv_data);
+       return;
+   }
 
-	while(1)
-	{
-		bytes_received = recv(sock, recv_data, 1024, 0);
-		if (bytes_received < 0)
-		{
-		    lwip_close(sock);
+   while(1)
+   {
+       /* 从sock连接中接收最大1024字节数据 */
+       bytes_received = recv(sock, recv_data, 1024, 0);
+       if (bytes_received < 0)
+       {
+           /* 接收失败，关闭这个连接 */
+           lwip_close(sock);
 
-            /* release recv buffer */
-            rt_free(recv_data);
-			break;
-		}
+           /* 释放接收缓冲 */
+           rt_free(recv_data);
+           break;
+       }
 
-		recv_data[bytes_received] = '\0';
+       /* 有接收到数据，把末端清零 */
+       recv_data[bytes_received] = '\0';
 
-		if (strcmp(recv_data , "q") == 0 || strcmp(recv_data , "Q") == 0)
-		{
-			lwip_close(sock);
+       if (strcmp(recv_data , "q") == 0 || strcmp(recv_data , "Q") == 0)
+       {
+           /* 如果是首字母是q或Q，关闭这个连接 */
+           lwip_close(sock);
 
-            /* release recv buffer */
-            rt_free(recv_data);
-			break;
-		}
-		else
-		{
-			rt_kprintf("\nRecieved data = %s " , recv_data);
-		}
+           /* 释放接收缓冲 */
+           rt_free(recv_data);
+           break;
+       }
+       else
+       {
+           /* 在控制终端显示收到的数据 */
+           rt_kprintf("\nRecieved data = %s " , recv_data);
+       }
 
-		send(sock,send_data,strlen(send_data), 0);
-	}
+       /* 发送数据到sock连接 */
+       send(sock,send_data,strlen(send_data), 0);
+   }
 
-	return;
+   return;
 }
 
 #ifdef RT_USING_FINSH
 #include <finsh.h>
+/* 输出tcpclient函数到finsh shell中 */
 FINSH_FUNCTION_EXPORT(tcpclient, startup tcp client);
 #endif
diff --git a/examples/network/tcpserver.c b/examples/network/tcpserver.c
index 606e842c8d..9fa7bc8fb8 100644
--- a/examples/network/tcpserver.c
+++ b/examples/network/tcpserver.c
@@ -1,109 +1,122 @@
 #include <rtthread.h>
-#include <lwip/sockets.h>
+#include <lwip/sockets.h> /* 使用BSD Socket接口必须包含sockets.h这个头文件 */
 
-static const char send_data[] = "This is TCP Server from RT-Thread.";
+static const char send_data[] = "This is TCP Server from RT-Thread."; /* 发送用到的数据 */
 void tcpserv(void* parameter)
 {
-	char *recv_data;
-	rt_uint32_t sin_size;
-	int sock, connected, bytes_received;
-	struct sockaddr_in server_addr, client_addr;
-    rt_bool_t stop = RT_FALSE;
+   char *recv_data; /* 用于接收的指针，后面会做一次动态分配以请求可用内存 */
+   rt_uint32_t sin_size;
+   int sock, connected, bytes_received;
+   struct sockaddr_in server_addr, client_addr;
+   rt_bool_t stop = RT_FALSE; /* 停止标志 */
 
-    recv_data = rt_malloc(1024);
-    if (recv_data == RT_NULL)
-    {
-        rt_kprintf("No memory\n");
-        return;
-    }
+   recv_data = rt_malloc(1024); /* 分配接收用的数据缓冲 */
+   if (recv_data == RT_NULL)
+   {
+       rt_kprintf("No memory\n");
+       return;
+   }
 
-    /* create a socket */
-	if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
-	{
-		rt_kprintf("Socket error\n");
+   /* 一个socket在使用前，需要预先创建出来，指定SOCK_STREAM为TCP的socket */
+   if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
+   {
+       /* 创建失败的错误处理 */
+       rt_kprintf("Socket error\n");
 
-        /* release recv buffer */
-        rt_free(recv_data);
-		return;
-	}
+       /* 释放已分配的接收缓冲 */
+       rt_free(recv_data);
+       return;
+   }
 
-    /* init server address */
-	server_addr.sin_family = AF_INET;
-	server_addr.sin_port = htons(5000);
-	server_addr.sin_addr.s_addr = INADDR_ANY;
-	rt_memset(&(server_addr.sin_zero),8, sizeof(server_addr.sin_zero));
+   /* 初始化服务端地址 */
+   server_addr.sin_family = AF_INET;
+   server_addr.sin_port = htons(5000); /* 服务端工作的端口 */
+   server_addr.sin_addr.s_addr = INADDR_ANY;
+   rt_memset(&(server_addr.sin_zero),8, sizeof(server_addr.sin_zero));
 
-    /* bind socket */
-	if (bind(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
-	{
-		rt_kprintf("Unable to bind\n");
+   /* 绑定socket到服务端地址 */
+   if (bind(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
+   {
+       /* 绑定失败 */
+       rt_kprintf("Unable to bind\n");
 
-        /* release recv buffer */
-        rt_free(recv_data);
-		return;
-	}
+       /* 释放已分配的接收缓冲 */
+       rt_free(recv_data);
+       return;
+   }
 
-    /* listen socket */
-	if (listen(sock, 5) == -1)
-	{
-		rt_kprintf("Listen error\n");
+   /* 在socket上进行监听 */
+   if (listen(sock, 5) == -1)
+   {
+       rt_kprintf("Listen error\n");
 
-        /* release recv buffer */
-        rt_free(recv_data);
-		return;
-	}
+       /* release recv buffer */
+       rt_free(recv_data);
+       return;
+   }
 
-	rt_kprintf("\nTCPServer Waiting for client on port 5000...\n");
-	while(stop != RT_TRUE)
-	{
-		sin_size = sizeof(struct sockaddr_in);
+   rt_kprintf("\nTCPServer Waiting for client on port 5000...\n");
+   while(stop != RT_TRUE)
+   {
+       sin_size = sizeof(struct sockaddr_in);
 
-        /* accept a client socket */
-		connected = accept(sock, (struct sockaddr *)&client_addr, &sin_size);
+       /* 接受一个客户端连接socket的请求，这个函数调用是阻塞式的 */
+       connected = accept(sock, (struct sockaddr *)&client_addr, &sin_size);
+       /* 返回的是连接成功的socket */
 
-		rt_kprintf("I got a connection from (%s , %d)\n",
-			   inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port));
+       /* 接受返回的client_addr指向了客户端的地址信息 */
+       rt_kprintf("I got a connection from (%s , %d)\n",
+                  inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port));
 
-		while (1)
-		{
-            send(connected, send_data, strlen(send_data), 0);
+       /* 客户端连接的处理 */
+       while (1)
+       {
+           /* 发送数据到connected socket */
+           send(connected, send_data, strlen(send_data), 0);
 
-			bytes_received = recv(connected,recv_data, 1024, 0);
-			if (bytes_received < 0)
-			{
-			    /* close socket */
-			    lwip_close(connected);
-			    break;
-			}
+           /* 从connected socket中接收数据，接收buffer是1024大小，但并不一定能够收到1024大小的数据 */
+           bytes_received = recv(connected,recv_data, 1024, 0);
+           if (bytes_received < 0)
+           {
+               /* 接收失败，关闭这个connected socket */
+               lwip_close(connected);
+               break;
+           }
 
-			recv_data[bytes_received] = '\0';
-			if (strcmp(recv_data , "q") == 0 || strcmp(recv_data , "Q") == 0)
-			{
-				lwip_close(connected);
-				break;
-			}
-			else if (strcmp(recv_data, "exit") == 0)
-			{
-			    lwip_close(connected);
-			    stop = RT_TRUE;
-			    break;
-			}
-			else
-			{
-				rt_kprintf("RECIEVED DATA = %s \n" , recv_data);
-			}
-		}
-	}
+           /* 有接收到数据，把末端清零 */
+           recv_data[bytes_received] = '\0';
+           if (strcmp(recv_data , "q") == 0 || strcmp(recv_data , "Q") == 0)
+           {
+               /* 如果是首字母是q或Q，关闭这个连接 */
+               lwip_close(connected);
+               break;
+           }
+           else if (strcmp(recv_data, "exit") == 0)
+           {
+               /* 如果接收的是exit，则关闭整个服务端 */
+               lwip_close(connected);
+               stop = RT_TRUE;
+               break;
+           }
+           else
+           {
+               /* 在控制终端显示收到的数据 */
+               rt_kprintf("RECIEVED DATA = %s \n" , recv_data);
+           }
+       }
+   }
 
-	lwip_close(sock);
+   /* 退出服务 */
+   lwip_close(sock);
 
-	/* release recv buffer */
-	rt_free(recv_data);
+   /* 释放接收缓冲 */
+   rt_free(recv_data);
 
-	return ;
+   return ;
 }
 
 #ifdef RT_USING_FINSH
 #include <finsh.h>
+/* 输出tcpserv函数到finsh shell中 */
 FINSH_FUNCTION_EXPORT(tcpserv, startup tcp server);
 #endif
diff --git a/examples/network/udpclient.c b/examples/network/udpclient.c
index 5634627cdb..041adb32c5 100644
--- a/examples/network/udpclient.c
+++ b/examples/network/udpclient.c
@@ -1,42 +1,50 @@
 #include <rtthread.h>
-#include <lwip/netdb.h>
-#include <lwip/sockets.h>
+#include <lwip/netdb.h> /* 为了解析主机名，需要包含netdb.h头文件 */
+#include <lwip/sockets.h> /* 使用BSD socket，需要包含sockets.h头文件 */
 
-const char send_data[] = "This is UDP Client from RT-Thread.\n";
+const char send_data[] = "This is UDP Client from RT-Thread.\n"; /* 发送用到的数据 */
 void udpclient(const char* url, int port, int count)
 {
-	int sock;
-	struct hostent *host;
-	struct sockaddr_in server_addr;
+   int sock;
+   struct hostent *host;
+   struct sockaddr_in server_addr;
 
-	host= (struct hostent *) gethostbyname(url);
+   /* 通过函数入口参数url获得host地址（如果是域名，会做域名解析） */
+   host= (struct hostent *) gethostbyname(url);
 
-	if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
-	{
-		rt_kprintf("Socket error\n");
-		return;
-	}
+   /* 创建一个socket，类型是SOCK_DGRAM，UDP类型 */
+   if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
+   {
+       rt_kprintf("Socket error\n");
+       return;
+   }
 
-	server_addr.sin_family = AF_INET;
-	server_addr.sin_port = htons(port);
-	server_addr.sin_addr = *((struct in_addr *)host->h_addr);
-	rt_memset(&(server_addr.sin_zero), 0, sizeof(server_addr.sin_zero));
+   /* 初始化预连接的服务端地址 */
+   server_addr.sin_family = AF_INET;
+   server_addr.sin_port = htons(port);
+   server_addr.sin_addr = *((struct in_addr *)host->h_addr);
+   rt_memset(&(server_addr.sin_zero), 0, sizeof(server_addr.sin_zero));
 
-	while (count)
-	{
-		sendto(sock, send_data, strlen(send_data), 0,
-		   (struct sockaddr *)&server_addr, sizeof(struct sockaddr));
+   /* 总计发送count次数据 */
+   while (count)
+   {
+       /* 发送数据到服务远端 */
+       sendto(sock, send_data, strlen(send_data), 0,
+              (struct sockaddr *)&server_addr, sizeof(struct sockaddr));
 
-        rt_thread_delay(50);
+       /* 线程休眠一段时间 */
+       rt_thread_delay(50);
 
-        count --;
-	}
+       /* 计数值减一 */
+       count --;
+   }
 
-    /* close socket */
-	lwip_close(sock);
+   /* 关闭这个socket */
+   lwip_close(sock);
 }
 
 #ifdef RT_USING_FINSH
 #include <finsh.h>
+/* 输出udpclient函数到finsh shell中 */
 FINSH_FUNCTION_EXPORT(udpclient, startup udp client);
 #endif
diff --git a/examples/network/udpserver.c b/examples/network/udpserver.c
index 9fede482fb..d480ff3d14 100644
--- a/examples/network/udpserver.c
+++ b/examples/network/udpserver.c
@@ -1,74 +1,84 @@
 #include <rtthread.h>
-#include <lwip/sockets.h>
+#include <lwip/sockets.h> /* 使用BSD socket，需要包含sockets.h头文件 */
 
 void udpserv(void* paramemter)
 {
-	int sock;
-	int bytes_read;
-	char *recv_data;
-	rt_uint32_t addr_len;
-	struct sockaddr_in server_addr , client_addr;
+   int sock;
+   int bytes_read;
+   char *recv_data;
+   rt_uint32_t addr_len;
+   struct sockaddr_in server_addr, client_addr;
 
-    recv_data = rt_malloc(1024);
-    if (recv_data == RT_NULL)
-    {
-        rt_kprintf("No memory\n");
-        return;
-    }
+   /* 分配接收用的数据缓冲 */
+   recv_data = rt_malloc(1024);
+   if (recv_data == RT_NULL)
+   {
+       /* 分配内存失败，返回 */
+       rt_kprintf("No memory\n");
+       return;
+   }
 
-    /* create socket */
-	if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
-	{
-		rt_kprintf("Socket error\n");
+   /* 创建一个socket，类型是SOCK_DGRAM，UDP类型 */
+   if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
+   {
+       rt_kprintf("Socket error\n");
 
-        /* release recv buffer */
-        rt_free(recv_data);
-		return;
-	}
+       /* 释放接收用的数据缓冲 */
+       rt_free(recv_data);
+       return;
+   }
 
-    /* init server socket address */
-	server_addr.sin_family = AF_INET;
-	server_addr.sin_port = htons(5000);
-	server_addr.sin_addr.s_addr = INADDR_ANY;
-	rt_memset(&(server_addr.sin_zero),0, sizeof(server_addr.sin_zero));
+   /* 初始化服务端地址 */
+   server_addr.sin_family = AF_INET;
+   server_addr.sin_port = htons(5000);
+   server_addr.sin_addr.s_addr = INADDR_ANY;
+   rt_memset(&(server_addr.sin_zero),0, sizeof(server_addr.sin_zero));
 
-	if (bind(sock,(struct sockaddr *)&server_addr,
-			 sizeof(struct sockaddr)) == -1)
-	{
-		rt_kprintf("Bind error\n");
+   /* 绑定socket到服务端地址 */
+   if (bind(sock,(struct sockaddr *)&server_addr,
+            sizeof(struct sockaddr)) == -1)
+   {
+       /* 绑定地址失败 */
+       rt_kprintf("Bind error\n");
 
-        /* release recv buffer */
-        rt_free(recv_data);
-        return;
-	}
+       /* 释放接收用的数据缓冲 */
+       rt_free(recv_data);
+       return;
+   }
 
-	addr_len = sizeof(struct sockaddr);
+   addr_len = sizeof(struct sockaddr);
+   rt_kprintf("UDPServer Waiting for client on port 5000...\n");
 
-	rt_kprintf("UDPServer Waiting for client on port 5000...\n");
+   while (1)
+   {
+       /* 从sock中收取最大1024字节数据 */
+       bytes_read = recvfrom(sock, recv_data, 1024, 0,
+                             (struct sockaddr *)&client_addr, &addr_len);
+       /* UDP不同于TCP，它基本不会出现收取的数据失败的情况，除非设置了超时等待 */
 
-	while (1)
-	{
-		bytes_read = recvfrom(sock, recv_data, 1024, 0,
-            (struct sockaddr *)&client_addr, &addr_len);
-		recv_data[bytes_read] = '\0';
-		rt_kprintf("\n(%s , %d) said : ",inet_ntoa(client_addr.sin_addr),
-			   ntohs(client_addr.sin_port));
-		rt_kprintf("%s", recv_data);
+       recv_data[bytes_read] = '\0'; /* 把末端清零 */
 
-        if (strcmp(recv_data, "exit") == 0)
-        {
-            lwip_close(sock);
+       /* 输出接收的数据 */
+       rt_kprintf("\n(%s , %d) said : ",inet_ntoa(client_addr.sin_addr),
+                  ntohs(client_addr.sin_port));
+       rt_kprintf("%s", recv_data);
 
-            /* release recv buffer */
-            rt_free(recv_data);
-            break;
-        }
-	}
+       /* 如果接收数据是exit，退出 */
+       if (strcmp(recv_data, "exit") == 0)
+       {
+           lwip_close(sock);
 
-	return;
+           /* 释放接收用的数据缓冲 */
+           rt_free(recv_data);
+           break;
+       }
+   }
+
+   return;
 }
 
 #ifdef RT_USING_FINSH
 #include <finsh.h>
+/* 输出udpserv函数到finsh shell中 */
 FINSH_FUNCTION_EXPORT(udpserv, startup udp server);
 #endif