FreeRTOS_DNS.h
BaseType_t FreeRTOS_getaddrinfo_a( const char * pcName,
const char * pcService,
const struct freertos_addrinfo * pxHints,
struct freertos_addrinfo ** ppxResult,
FOnDNSEvent pCallback,
void * pvSearchID,
TickType_t uxTimeout );
The suffix "_a" stands for asynchronous, and the function is a non-blocking function. The API functionality
is the same as FreeRTOS_getaddrinfo,
along with the capability to perform multiple IP lookups asynchronously. Which means the call returns immediately
whereas the lookup happens in the background. Once the lookup is completed or a timeout occurs, a user defined
function pCallback will be called to send the updated results back.
Parameters:
- pcName
- The name of the node or device.
- pcService
- Ignored for now.
- pxHints
- If not NULL then can be used to indicate the preferred type of IP ( v4 or v6 ).
- ppxResult
- An allocated struct, containing the results.
- pCallback
- The callback function to be called when the address has been found or when a timeout has been reached.
- pvSearchID
- Search ID for the callback function.
- uxTimeout
- Timeout for the callback function.
The callback function should be of the following type:
void (* FOnDNSEvent ) ( const char * ,
void * ,
struct freertos_addrinfo * );
where the
pcName is the name of the node or device that's looked up,
pvSearchID
is the ID that was passed when the call to
FreeRTOS_getaddrinfo_a was made for that query,
and
pxAddressInfo contains the result.
Example usage:
#include "FreeRTOS_DNS.h"
static BaseType_t xDNSResult = -2;
static void vDNSEvent( const char * pcName,
void * pvSearchID,
struct freertos_addrinfo * pxAddrInfo )
{
( void ) pcName;
( void ) pvSearchID;
FreeRTOS_printf( ( "vDNSEvent: called with %p\n", pxAddrInfo ) );
showAddressInfo( pxAddrInfo );
if( pxAddrInfo != NULL )
{
xDNSResult = 0;
}
}
static void dnsTest( const char * pcHostName )
{
uint32_t ulID;
BaseType_t rc;
if( xApplicationGetRandomNumber( &( ulID ) ) != pdFALSE )
{
FreeRTOS_dnsclear();
xDNSResult = -2;
rc = FreeRTOS_getaddrinfo_a( pcHostName,
NULL,
&xHints,
&pxResult,
vDNSEvent,
( void * ) ulID,
pdMS_TO_TICKS( 1000U ) );
vTaskDelay( pdMS_TO_TICKS( 1000U ) );
rc = xDNSResult;
FreeRTOS_printf( ( "Lookup '%s': %d\n", pcHostName, rc ) );
}
else
{
FreeRTOS_printf( ( "dns_test: Failed to generate a random SearchID\n" ) );
}
}
Example use of the FreeRTOS_getaddrinfo_a() API function
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