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FreeRTOS+TCP V2 is now included in the main FreeRTOS kernel download under the MIT license.

Sending Data Using a TCP Socket
Part of the FreeRTOS+TCP Networking Tutorial

[Note: This page does not describe the callback or zero copy interfaces, which are available for expert users.]

After a TCP socket has been created, configured, and bound it can be connected to a remote socket using the FreeRTOS_connect() API function, or it can accept connections from a remote socket. Once connected, data is sent to the remote socket using the FreeRTOS_send() API function.

The source code below shows a function that creates a socket, sends data to the socket, then gracefully shuts down and closes the socket. Note that this socket is not explicitly bound to a port number - causing it to be bound automatically inside the FreeRTOS_connect() API function.


void vTCPSend( char char *pcBufferToTransmit, const size_t xTotalLengthToSend )
{
Socket_t xSocket;
struct freertos_sockaddr xRemoteAddress;
BaseType_t xAlreadyTransmitted = 0, xBytesSent = 0;
TaskHandle_t xRxTask = NULL;
size_t xLenToSend;

    /* Set the IP address (192.168.0.50) and port (1500) of the remote socket
    to which this client socket will transmit. */
    xRemoteAddress.sin_port = FreeRTOS_htons( 15000 );
    xRemoteAddress.sin_addr = FreeRTOS_inet_addr_quick( 192, 168, 0 200 );

    /* Create a socket. */
    xSocket = FreeRTOS_socket( FREERTOS_AF_INET,
                               FREERTOS_SOCK_STREAM,/* FREERTOS_SOCK_STREAM for TCP. */
                               FREERTOS_IPPROTO_TCP );
    configASSERT( xSocket != FREERTOS_INVALID_SOCKET );

    /* Connect to the remote socket.  The socket has not previously been bound to
    a local port number so will get automatically bound to a local port inside
    the FreeRTOS_connect() function. */
    if( FreeRTOS_connect( xSocket, &xRemoteAddress, sizeof( xRemoteAddress ) ) == 0 )
    {
        /* Keep sending until the entire buffer has been sent. */
        while( xAlreadyTransmitted < xTotalLengthToSend )
        {
            /* How many bytes are left to send? */
            xLenToSend = xTotalLengthToSend - xAlreadyTransmitted;
            xBytesSent = FreeRTOS_send( /* The socket being sent to. */
                                        xSocket,
                                        /* The data being sent. */
                                        &( pcBufferToTransmit[ xAlreadyTransmitted ] ),
                                        /* The remaining length of data to send. */
                                        xLenToSend,
                                        /* ulFlags. */
                                        0 );

            if( xBytesSent >= 0 )
            {
                /* Data was sent successfully. */
                xAlreadyTransmitted += xBytesSent;
            }
            else
            {
                /* Error - break out of the loop for graceful socket close. */
                break;
            }
        }
    }

    /* Initiate graceful shutdown. */
    FreeRTOS_shutdown( xSocket, FREERTOS_SHUT_RDWR );

    /* Wait for the socket to disconnect gracefully (indicated by FreeRTOS_recv()
    returning a FREERTOS_EINVAL error) before closing the socket. */
    while( FreeRTOS_recv( xSocket, pcBufferToTransmit, xTotalLengthToSend, 0 ) >= 0 )
    {
        /* Wait for shutdown to complete.  If a receive block time is used then
        this delay will not be necessary as FreeRTOS_recv() will place the RTOS task
        into the Blocked state anyway. */
        vTaskDelay( pdTICKS_TO_MS( 250 ) );

        /* Note - real applications should implement a timeout here, not just
        loop forever. */
    }

    /* The socket has shut down and is safe to close. */
    FreeRTOS_closesocket( xSocket );
}
						
Example using FreeRTOS_send()



<< Back to the RTOS TCP networking tutorial index


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