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

The FreeRTOS_sendto() TCP/IP stack API function is used to send data to a UDP socket. Data can only be sent after the socket has been created, configured, and optionally bound to a local port number.

As detailed on the FreeRTOS_sendto() API reference page, FreeRTOS_sendto() 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 UDP socket before entering a loop that sends a string to the socket (using the standard calling semantics) every 1 second (1000ms). The comments in the source code example provide more information.

static void vUDPSendUsingStandardInterface( void *pvParameters )
Socket_t xSocket;
struct freertos_sockaddr xDestinationAddress;
uint8_t cString[ 50 ];
uint32_t ulCount = 0UL;
const TickType_t x1000ms = 1000UL / portTICK_PERIOD_MS;

   /* Send strings to port 10000 on IP address */
   xDestinationAddress.sin_addr = FreeRTOS_inet_addr( "" );
   xDestinationAddress.sin_port = FreeRTOS_htons( 10000 );

   /* Create the socket. */
   xSocket = FreeRTOS_socket( FREERTOS_AF_INET,
                              FREERTOS_SOCK_DGRAM,/*FREERTOS_SOCK_DGRAM for UDP.*/
                              FREERTOS_IPPROTO_UDP );

   /* Check the socket was created. */

   /* NOTE: FreeRTOS_bind() is not called.  This will only work if
   ipconfigALLOW_SOCKET_SEND_WITHOUT_BIND is set to 1 in FreeRTOSIPConfig.h. */

   for( ;; )
       /* Create the string that is sent. */
       sprintf( cString,
                "Standard send message number %lu\r\n",
                ulCount );

       /* Send the string to the UDP socket.  ulFlags is set to 0, so the standard
       semantics are used.  That means the data from cString[] is copied
       into a network buffer inside FreeRTOS_sendto(), and cString[] can be
       reused as soon as FreeRTOS_sendto() has returned. */
       FreeRTOS_sendto( xSocket,
                        strlen( cString ),
                        sizeof( xDestinationAddress ) );


       /* Wait until it is time to send again. */
       vTaskDelay( x1000ms );
Example using FreeRTOS_sendto() with the standard (as opposed to zero copy) calling semantics

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