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FreeRTOS+TCP is still in the lab
FreeRTOS+TCP is already used in commercial products and we encourage you to try it yourself. Be aware however that we are still refining its design, and the source code and documentation do not yet meet Real Time Engineers Ltd's strict quality standards.
Please use the forum for support, feedback and ideas, or contact us directly if you have a specific business interest.

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 ( 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 );

    /* 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. */
                                        /* The data being sent. */
                                        &( pcBufferToTransmit[ xAlreadyTransmitted ] ),
                                        /* The remaining length of data to send. */
                                        /* ulFlags. */
                                        0 );

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

    /* 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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