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DNS Resolving in MFC

How do you resolve a DNS address in MFC?  Do you need to do it in API.  I need source code to support this theory.  Can any one give me any source code in either MFC or the API?
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dbetz
Asked:
dbetz
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1 Solution
 
jhanceCommented:
// First, initialize the WINSOCK interface
WORD wVersionRequested;
WSADATA wsaData;
int err;
HOSTENT *hostent;

wVersionRequested = MAKEWORD( 2, 0 );
err = WSAStartup( wVersionRequested, &wsaData );
if ( err != 0 ) {
      /* Tell the user that we could not find a usable */
      /* WinSock DLL.                                  */    
      AfxMessageBox("ERROR: Failed to initialize WINSOCK", MB_OK);
      return;
}


// Do a DNS lookup of a hostname from it's IP
CString ip("192.168.0.10");
unsigned long ipaddr = inet_addr((LPCTSTR)ip);
hostent = gethostbyaddr((char *)&ipaddr, 4, AF_INET);
if(hostent != NULL){
      ip = CString(hostent->h_name);
}
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dbetzAuthor Commented:
No, I need the MFC code to get the IP from a hostname.  Do you have any MFC code?
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jhanceCommented:
The above code is in MFC but gives you the hostname from the IP address.  To do the other lookup, use the gethostbyname() function.  The code would be very similar but would have:

CString hostaddr;

hostent = gethostbyname(hostname);
hostaddr = CString(hostent->h_addr_list);


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dbetzAuthor Commented:
Can you put that in the entire code for me, and no that is not MFC, that is API code...But that is alright.
0
 
jhanceCommented:
// First, initialize the WINSOCK interface
WORD wVersionRequested;
WSADATA wsaData;
int err;
HOSTENT *hostent;

wVersionRequested = MAKEWORD( 2, 0 );
err = WSAStartup( wVersionRequested, &wsaData );
if ( err != 0 ) {
/* Tell the user that we could not find a usable */
/* WinSock DLL. */
AfxMessageBox("ERROR: Failed to initialize WINSOCK", MB_OK);
return;
}


// Do a DNS lookup of an IP from it's hostname
CString hostnm("fred.bob.com");
hostent = gethostbyname((LPCTSTR)hostnm);
if(hostent != NULL){
hostnm = CString(hostent->h_addr_list);
}
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dbetzAuthor Commented:
I get this error this this code, it is at this line...It looks as though it is trying to convert an array to a CString.

"hostnm = CString(hostent->h_addr_list);"

error C2665: 'CString::CString' : none of the 7 overloads can convert parameter 1 from type 'char ** ' (new behavior; please see help)
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jhanceCommented:
Sorry, mental lapse occurred :-{

hostnm = CString(hostent->h_addr_list[0]);"
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dbetzAuthor Commented:
That is to return an IP then?  All I get is garble with the host name: ÌGÈJwww.yahoo.com

And the same garble everytime...and it does not access the Internet anymore.  The IP->Host worked though.
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jhanceCommented:
OK, I stopped trying to do it from memory.  Following is a complete program that you can compile and run:

#include <stdio.h>
#include <winsock.h>

void main()
{
 // First, initialize the WINSOCK interface
 WORD wVersionRequested;
 WSADATA wsaData;
 int err;
 HOSTENT *hostent;
 IN_ADDR in_addr;

 wVersionRequested = MAKEWORD( 2, 0 );
 err = WSAStartup( wVersionRequested, &wsaData );
 if ( err != 0 ) {
 /* Tell the user that we could not find a usable */
 /* WinSock DLL. */
 printf("ERROR: Failed to initialize WINSOCK");
 return;
 }


 // Do a DNS lookup of an IP from it's hostname
 hostent = gethostbyname("www.yahoo.com");
 if(hostent != NULL){
  memcpy(&in_addr, hostent->h_addr_list[0], 4);
  printf("www.yahoo.com = %s\n", inet_ntoa(in_addr));
 }
 else{
  printf("Error, lookup failed\n");
 }
}
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dbetzAuthor Commented:
Thank you, it works fine now.
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