coreHTTP 演示（相互身份验证）

static void prvHTTPDemoTask( void * pvParameters )

{

    /* The transport layer interface used by the HTTP Client library. */

    TransportInterface_t xTransportInterface;

    /* The network context for the transport layer interface. */

    NetworkContext_t xNetworkContext = { 0 };

    TlsTransportParams_t xTlsTransportParams = { 0 };

    BaseType_t xIsConnectionEstablished = pdFALSE;



    /* The user of this demo must check the logs for any failure codes. */

    BaseType_t xDemoStatus = pdPASS;



    /* Remove compiler warnings about unused parameters. */

    ( void ) pvParameters;



    /* Set the pParams member of the network context with desired transport. */

    xNetworkContext.pParams = &xTlsTransportParams



    /**************************** Connect. ******************************/



    /* Attempt to connect to the HTTP server. If connection fails, retry after a


     * timeout. The timeout value will be exponentially increased until either the


     * maximum number of attempts or the maximum timeout value is reached. The


     * function returns pdFAIL if the TCP connection cannot be established with


     * the server after configured number of attempts. */

    xDemoStatus = connectToServerWithBackoffRetries( prvConnectToServer,

                                                     &xNetworkContext );



    if( xDemoStatus == pdPASS )

    {

        /* Set a flag indicating that a TLS connection exists. */

        xIsConnectionEstablished = pdTRUE;



        /* Define the transport interface. */

        xTransportInterface.pNetworkContext = &xNetworkContext

        xTransportInterface.send = TLS_FreeRTOS_send;

        xTransportInterface.recv = TLS_FreeRTOS_recv;

    }

    else

    {

        /* Log error to indicate connection failure after all


         * reconnect attempts are over. */

        LogError( ( "Failed to connect to HTTP server %.*s.",

                    ( int32_t ) AWS_IOT_ENDPOINT_LENGTH,

                    democonfigAWS_IOT_ENDPOINT ) );

    }



    /*********************** Send HTTP request.************************/



    if( xDemoStatus == pdPASS )

    {

        xDemoStatus = prvSendHttpRequest( &xTransportInterface,

                                          HTTP_METHOD_POST,

                                          ( sizeof( HTTP_METHOD_POST ) - 1 ),

                                          democonfigPOST_PATH,

                                          ( sizeof( democonfigPOST_PATH ) - 1 ) );

    }



    /**************************** Disconnect. ******************************/



    /* Close the network connection to clean up any system resources that the


     * demo may have consumed. */

    if( xIsConnectionEstablished == pdTRUE )

    {

        /* Close the network connection.  */

        TLS_FreeRTOS_Disconnect( &xNetworkContext );

    }



    if( xDemoStatus == pdPASS )

    {

        LogInfo( ( "prvHTTPDemoTask() completed successfully. "

                   "Total free heap is %u.\r\n",

                   xPortGetFreeHeapSize() ) );

        LogInfo( ( "Demo completed successfully.\r\n" ) );

    }

}

BaseType_t connectToServerWithBackoffRetries( TransportConnect_t connectFunction,

                                              NetworkContext_t * pxNetworkContext )

{

    BaseType_t xReturn = pdFAIL;

    /* Status returned by the retry utilities. */

    BackoffAlgorithmStatus_t xBackoffAlgStatus = BackoffAlgorithmSuccess;

    /* Struct containing the next backoff time. */

    BackoffAlgorithmContext_t xReconnectParams;

    uint16_t usNextBackoff = 0U;



    assert( connectFunction != NULL );



    /* Initialize reconnect attempts and interval */

    BackoffAlgorithm_InitializeParams( &xReconnectParams,

                                       RETRY_BACKOFF_BASE_MS,

                                       RETRY_MAX_BACKOFF_DELAY_MS,

                                       RETRY_MAX_ATTEMPTS );



    /* Attempt to connect to the HTTP server. If connection fails, retry after a


     * timeout. The timeout value will exponentially increase until either the


     * maximum timeout value is reached or the set number of attempts are


     * exhausted.*/

    do

    {

        xReturn = connectFunction( pxNetworkContext );



        if( xReturn != pdPASS )

        {

            LogWarn( ( "Connection to the HTTP server failed. "

                       "Retrying connection with backoff and jitter." ) );

            LogInfo( ( "Retry attempt %lu out of maximum retry attempts %lu.",

                       ( xReconnectParams.attemptsDone + 1 ),

                         RETRY_MAX_ATTEMPTS ) );



            /* Generate a random number and calculate backoff value (in milliseconds) for


             * the next connection retry.


             * Note: It is recommended to seed the random number generator with a device-specific


             * entropy source so that possibility of multiple devices retrying failed network operations


             * at similar intervals can be avoided. */

            xBackoffAlgStatus = BackoffAlgorithm_GetNextBackoff( &xReconnectParams, uxRand(), &usNextBackoff );

        }

    } while( ( xReturn == pdFAIL ) && ( xBackoffAlgStatus == BackoffAlgorithmSuccess ) );



    if( xReturn == pdFAIL )

    {

        LogError( ( "Connection to the server failed, all attempts exhausted." ) );

    }



    return xReturn;

}

static BaseType_t prvConnectToServer( NetworkContext_t * pxNetworkContext )

{

    BaseType_t xStatus = pdPASS;



    TlsTransportStatus_t xNetworkStatus;

    NetworkCredentials_t xNetworkCredentials = { 0 };



    configASSERT( pxNetworkContext != NULL );



    if( democonfigAWS_HTTP_PORT == 443 )

    {

        /* ALPN protocols must be a NULL-terminated list of strings. Therefore,


         * the first entry will contain the actual ALPN protocol string while the


         * second entry must remain NULL. */

        static const char * pcAlpnProtocols[] = { IOT_CORE_ALPN_PROTOCOL_NAME, NULL };

        xNetworkCredentials.pAlpnProtos = pcAlpnProtocols;

    }



    xNetworkCredentials.disableSni = democonfigDISABLE_SNI;

    /* Set the credentials for establishing a TLS connection. */

    xNetworkCredentials.pRootCa = ( const unsigned char * ) democonfigROOT_CA_PEM;

    xNetworkCredentials.rootCaSize = sizeof( democonfigROOT_CA_PEM );

    xNetworkCredentials.pClientCert = ( const unsigned char * ) democonfigCLIENT_CERTIFICATE_PEM;

    xNetworkCredentials.clientCertSize = sizeof( democonfigCLIENT_CERTIFICATE_PEM );

    xNetworkCredentials.pPrivateKey = ( const unsigned char * ) democonfigCLIENT_PRIVATE_KEY_PEM;

    xNetworkCredentials.privateKeySize = sizeof( democonfigCLIENT_PRIVATE_KEY_PEM );



    /* Establish a TLS session with the HTTP server. This example connects to


     * the HTTP server as specified in democonfigAWS_IOT_ENDPOINT and


     * democonfigAWS_HTTP_PORT in demo_config.h. */

    LogInfo( ( "Establishing a TLS session to %.*s:%d.",

               ( int32_t ) AWS_IOT_ENDPOINT_LENGTH,

               democonfigAWS_IOT_ENDPOINT,

               democonfigAWS_HTTP_PORT ) );



    /* Attempt to create a mutually authenticated TLS connection. */

    xNetworkStatus = TLS_FreeRTOS_Connect( pxNetworkContext,

                                           democonfigAWS_IOT_ENDPOINT,

                                           democonfigAWS_HTTP_PORT,

                                           &xNetworkCredentials,

                                           democonfigTRANSPORT_SEND_RECV_TIMEOUT_MS,

                                           democonfigTRANSPORT_SEND_RECV_TIMEOUT_MS );



    if( xNetworkStatus != TLS_TRANSPORT_SUCCESS )

    {

        xStatus = pdFAIL;

    }



    return xStatus;

}