接收 UDP 数据（标准接口）
FreeRTOS-Plus-TCP 网络教程节选

正如 FreeRTOS_recvfrom()() API 引用页面所述，FreeRTOS_recvfrom() 可以与标准调用语义或零拷贝调用语义一起使用。 本页演示的是标准调用语义。

下面的源代码片段显示了一个 RTOS 任务， 在进入使用标准调用语义（与零拷贝调用语义相反） 接收数据的循环之前，该任务会创建一个套接字。显示的是 IPv4 和 IPv6 用例。

IPv4

static void vUDPReceivingUsingStandardInterface( void *pvParameters )

{

long lBytes;

uint8_t cReceivedString[ 60 ];

struct freertos_sockaddr xClient, xBindAddress;

uint32_t xClientLength = sizeof( xClient );

Socket_t xListeningSocket;



   /* Attempt to open the socket. */

   xListeningSocket = FreeRTOS_socket( FREERTOS_AF_INET,

                                       FREERTOS_SOCK_DGRAM, /*FREERTOS_SOCK_DGRAM for UDP.*/

                                       FREERTOS_IPPROTO_UDP );



   /* Check the socket was created. */

   configASSERT( xListeningSocket != FREERTOS_INVALID_SOCKET );



   /* Bind to port 10000. */

   xBindAddress.sin_port = FreeRTOS_htons( 10000 );

   FreeRTOS_bind( xListeningSocket, &xBindAddress, sizeof( xBindAddress ) );



   for( ;; )

   {

       /* Receive data from the socket.  ulFlags is zero, so the standard

          interface is used.  By default the block time is portMAX_DELAY, but it

          can be changed using FreeRTOS_setsockopt(). */

       lBytes = FreeRTOS_recvfrom( xListeningSocket,

                                   cReceivedString,

                                   sizeof( cReceivedString ),

                                   0,

                                   &xClient,

                                   &xClientLength );



       if( lBytes > 0 )

       {

           /* Data was received and can be process here. */

       }

   }

}

使用 FreeRTOS_recvfrom() 与零拷贝（和标准相反）调用语义的示例

IPv6 -

static void vUDPReceivingUsingStandardInterface( void *pvParameters )

{

    long lBytes;

    uint8_t cReceivedString[ 60 ];

    struct freertos_sockaddr xClient, xBindAddress;

    uint32_t xClientLength = sizeof( xClient );

    Socket_t xListeningSocket;



   /* Attempt to open the socket. */

   xListeningSocket = FreeRTOS_socket( FREERTOS_AF_INET6, /* FREERTOS_AF_INET6 for IPv6 socket */

                                       FREERTOS_SOCK_DGRAM, /*FREERTOS_SOCK_DGRAM for UDP.*/

                                       FREERTOS_IPPROTO_UDP );



   /* Check the socket was created. */

   configASSERT( xListeningSocket != FREERTOS_INVALID_SOCKET );



   /* Bind to port 10000. */

   xBindAddress.sin_port = FreeRTOS_htons( 10000 );

   FreeRTOS_bind( xListeningSocket, &xBindAddress, sizeof( xBindAddress ) );



   for( ;; )

   {

       /* Receive data from the socket.  ulFlags is zero, so the standard


          interface is used.  By default the block time is portMAX_DELAY, but it


          can be changed using FreeRTOS_setsockopt(). */

       lBytes = FreeRTOS_recvfrom( xListeningSocket,

                                   cReceivedString,

                                   sizeof( cReceivedString ),

                                   0,

                                   &xClient,

                                   &xClientLength );



       if( lBytes > 0 )

       {

           /* Data was received and can be process here. */

       }

   }

}

使用 FreeRTOS_recvfrom() 与零拷贝（和标准相反）调用语义的示例

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