Código: Seleccionar todo

#include <windows.h> 
#include <windns.h>   
 
     // we need this API 
     
typedef int (WINAPI *DNSQUERYA)(PCSTR, WORD, DWORD, PIP4_ARRAY, PDNS_RECORD *, PVOID *); 
DNSQUERYA    _DnsQueryA; 

      // our procedures 
      
BOOL init_dns(void); 
BOOL MXLookup(char *, char *); 

int    main(void){ 
     if(init_dns() == FALSE){ 
        printf("exiting: could not locate APIs..."); 
        return 0; 
     } 
     
     char szDomain[] = "kefivx.info"; 
     char *szSMTP; 
     szSMTP = (char *) malloc(64);    // malloc some space 
     memset(szSMTP, 0, 64); 
     
     if(MXLookup(szDomain, szSMTP) == TRUE){    // perform lookup 
        printf("prefered SMTP server for '%s' is '%s'", szDomain, szSMTP); 
        return 1; 
     } 
        return 0; 
 } 
 
BOOL   init_dns(void){ 
     HINSTANCE hDNS; 
        
        // find dnsapi in memory 
        
        hDNS = GetModuleHandle("dnsapi"); 
        if(hDNS == 0){ 
                hDNS = LoadLibrary("dnsapi"); 
                if(hDNS == 0) 
                     return FALSE
  } 
        
        // find DnsQuery_A in memory 
        
        _DnsQueryA = (DNSQUERYA) GetProcAddress(hDNS, "DnsQuery_A"); 
        if(_DnsQueryA == 0) 
             return FALSE; 
        return TRUE; 
  } 
  
BOOL     MXLookup(char *szDomain, char *buffer){ 
     int   preference = 9001;   // OVER 9000 
     int   ret = 0; 
     
/* 
*   normally i would type this structure out myself... but i'm lazy and 
*   it's huge: http://msdn.microsoft.com/en-us/library/aa450351.aspx 
*/ 

     DNS_RECORD *pQueryResults; 
     DNS_RECORD *pQueryRec; 
     
     // make query 
     
     ret = _DnsQueryA(szDomain, DNS_TYPE_MX, DNS_QUERY_STANDARD, 0, &pQueryResults, 0); 
     if(ret != ERROR_SUCCESS) 
            return FALSE; 
            
     // sort through results to find lowest preference 
     
     for(pQueryRec = pQueryResults; pQueryRec; pQueryRec = pQueryRec->pNext){ 
         if(pQueryRec->wType != DNS_TYPE_MX) 
            continue; 
         if(pQueryRec->Data.MX.wPreference < preference){ 
            preference = pQueryRec->Data.MX.wPreference; 
            strcpy(buffer, pQueryRec->Data.MX.pNameExchange); 
         } 
      } 
      
      if(!buffer) 
         return FALSE; 
             return TRUE; 
 }