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Receiving UDP Data (standard interface)
Part of the FreeRTOS+TCP Networking Tutorial

The FreeRTOS_recvfrom() TCP/IP stack API function is used to receive from a UDP socket. Data can only be received after the socket has been created, configured, and bound to a local port number.

As detailed on the FreeRTOS_recvfrom() API reference page, FreeRTOS_recvfrom() can be used with standard calling semantics, or zero copy calling semantics. This page demonstrates the standard calling semantics.

The source code below shows a RTOS task that creates a socket before entering a loop that receives data using the standard (as opposed to zero copy) calling semantics.

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,
                                   sizeof( cReceivedString ),
                                   &xClientLength );

       if( lBytes > 0 )
           /* Data was received and can be process here. */
Example using FreeRTOS_recvfrom() with the standard (as opposed to zero copy) calling semantics

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