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FreeRTOS_SendPingRequest()
FreeRTOS_sockets.h
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| ulIPAddress |
The IP address to which the ping request is sent.
The IP address is expressed as a 32-bit number in network byte order.
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| xNumberOfBytesToSend |
The number of data bytes to send in the ping request.
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| xBlockTimeTicks |
The maximum time the calling task is prepared to wait
for a network buffer if one is not immediately available.
If a network buffer is not available then the calling task will be held in the Blocked state (so other tasks can execute) until either a buffer becomes available and therefore the ping request transmitted, or the block time expires. The block time is specified in ticks. Milliseconds can be converted to ticks by dividing the time in milliseconds by portTICK_PERIOD_MS.
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If a ping request is successfully sent then the sequence number sent in the ping message is returned to allow the application writer to match ping requests transmitted with ping replies received. See the example below.
If a ping request could not be sent then pdFAIL is returned.
Example usage:
This example defines two functions. vSendPing() transmits 8 bytes to a remote IP address. vApplicationPingReplyHook() is the standard FreeRTOS+UDP ping reply callback function. vApplicationPingReplyHook() receives the ping reply, then sends the received sequence number to vSendPing() where it is compared to the sequence number from the ping request.
/* FreeRTOS+UDP sockets include */ #define "FreeRTOS_sockets.h" /* This example code snippet assumes the queue has already been created! */ QueueHandle_t xPingReplyQueue; /* If ipconfigSUPPORT_OUTGOING_PINGS is set to 1 in FreeRTOSIPConfig.h then vApplicationPingReplyHook() is called by the IP stack when the stack receives a ping reply. void vApplicationPingReplyHook( ePingReplyStatus_t eStatus, uint16_t usIdentifier ) { switch( eStatus ) { case eSuccess : /* A valid ping reply has been received. Post the sequence number on the queue that is read by the vSendPing() function below. Do not wait more than 10ms trying to send the message if it cannot be sent immediately because this function is called from the IP stack task - blocking in this function will block the IP stack. */ xQueueSend( xPingReplyQueue, &usIdentifier, 10 / portTICK_PERIOD_MS ); break; case eInvalidChecksum : case eInvalidData : /* A reply was received but it was not valid. */ break; } } BaseType_t vSendPing( const int8_t *pcIPAddress ) { uint16_t usRequestSequenceNumber, usReplySequenceNumber; uint32_t ulIPAddress; /* The pcIPAddress parameter holds the destination IP address as a string in decimal dot notation (for example, "192.168.0.200"). Convert the string into the required 32-bit format. */ ulIPAddress = FreeRTOS_inet_addr( pcIPAddress ); /* Send a ping containing 8 data bytes. Wait (in the Blocked state) a maximum of 100ms for a network buffer into which the generated ping request can be written and sent. */ usRequestSequenceNumber = FreeRTOS_SendPingRequest( ulIPAddress, 8, 100 / portTICK_PERIOD_MS ); if( usRequestSequenceNumber == pdFAIL ) { /* The ping could not be sent because a network buffer could not be obtained within 100ms of FreeRTOS_SendPingRequest() being called. */ } else { /* The ping was sent. Wait 200ms for a reply. The sequence number from each reply is sent from the vApplicationPingReplyHook() on the xPingReplyQueue queue (this is not standard behaviour, but implemented in the example function above). It is assumed the queue was created before this function was called! */ if( xQueueReceive( xPingReplyQueue, &usReplySequenceNumber, 200 / portTICK_PERIOD_MS ) == pdPASS ) { /* A ping reply was received. Was it a reply to the ping just sent? */ if( usRequestSequenceNumber == usReplySequenceNumber ) { /* This was a reply to the request just sent. */ } } } }
Example use of the FreeRTOS_SendPingRequest() API function
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