The FreeRTOS Ecosystem Showcase . . .
A Selection of Add-on and Complementary Products

 Real time embedded FreeRTOS RSS feed 
Homepage FreeRTOS+ Products FreeRTOS Labs Support Forum Contact / Enquiries

 FreeRTOS+POSIX:
 POSIX API for FreeRTOS
 FreeRTOS+FAT:
 Thread aware file system

FreeRTOS+UDP was removed from the FreeRTOS kernel download from FreeRTOS V10.1.0. See the FreeRTOS+TCP stack, which can be configured for UDP only use, as an alternative.

FreeRTOS_gethostbyname()

[FreeRTOS Embedded IP Stack API]

FreeRTOS_sockets.h 
uint32_t FreeRTOS_gethostbyname( const uint8_t *pcHostName );

Performs a Domain Name System (DNS) lookup on a host name, returning the hosts IP address. For example, assuming a DNS server replies to the lookup request, a call to FreeRTOS_gethostbyname( "www.freertos.org" ) will return freertos.org's IP address.

ipconfigUSE_DNS must be set to 1 in FreeRTOSIPConfig.h for FreeRTOS_gethostbyname() to be available.

A DNS lookup can only be performed when FreeRTOS+UDP knows the IP address of a DNS server. If ipconfigUSE_DHCP is 0 in FreeRTOSIPConfig.h then the DNS server address is passed into FreeRTOS+UDP as a parameter of the FreeRTOS_IPInit() function. If ipconfigUSE_DHCP is 1 in FreeRTOSIPConfig.h then the DNS server address can be obtained from a DHCP server.

FreeRTOS_gethostbyname() will wait (in the Blocked state so other tasks can execute) for a reply for 200ms after each DNS request - with a maximum of 5 DNS requests being sent.

Parameters:

pcHostName   A standard NULL terminated string containing the name of the host being looked up.

Returns:

If the lookup is successful then the IP address of the host is returned in network byte order.

If the lookup fails then 0 is returned.

Example usage: 


/* FreeRTOS+UDP sockets include */
#define "FreeRTOS_sockets.h"

void aFunction( void )
{
uint32_t ulIPAddress;
int8_t cBuffer[ 16 ];

    /* Lookup the IP address of the FreeRTOS.org website. */
    ulIPAddress = FreeRTOS_gethostbyname( "www.freertos.org" );
    
    if( ulIPAddress != 0 )
    {
        /* Convert the IP address to a string. */
        FreeRTOS_inet_ntoa( ulIPAddress, ( char * ) cBuffer );
        
        /* Print out the IP address. */
        printf( "www.FreeRTOS.org is at IP address %s\r\n", cBuffer );
    }
    else
    {
        printf( "DNS lookup failed. " );
    }
}
Example use of the FreeRTOS_gethostbyname() API function


[ Back to the top ]    [ About FreeRTOS ]    [ Privacy ]    [ FreeRTOS+ Sitemap ]    [ Main FreeRTOS Sitemap ]    [ ]


Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.