gethostbyaddr() does not return any info

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3 total messages Started by Kris Tue, 15 May 2007 08:46

#1960

Author: Kris
Date: Tue, 15 May 2007 08:46

32 lines
1452 bytes

Hi,

I'm attempting to obtain the NetBIOS name of given IP address (which is 
a NAS device in my LAN).

However, the gethostbyaddr() call always returns NULL and the 
WSAGetLastError() returns 6 (=WSA_INVALID_HANDLE).

Does anybody know what I'm doing wrong ? The code below shows following 
output:

Address=1711280300
RemoteHost=00000000
Error=6

struct hostent* RemoteHost;
unsigned int Address;
char host_name[]="172.16.0.102";

Address=inet_addr(host_name);
DEBUG("Address=%d",Address);

RemoteHost=gethostbyaddr((char*)&Address,4,AF_INET);
DEBUG("RemoteHost=%08X",RemoteHost);

int Error=WSAGetLastError();
DEBUG("Error=%d",Error);


Thanks,

Kris

Re: gethostbyaddr() does not return any info

#1961

Author: Hans Galema
Date: Tue, 15 May 2007 09:35

36 lines
1907 bytes

Kris wrote:

> Does anybody know what I'm doing wrong ? 

You forgot to initialise.

The Windows Sockets WSAStartup function initiates use of the Windows Sockets DLL by a process

> char host_name[]="172.16.0.102";

How terrible to call an ip-address a hostname!

Add some code before and afther what you already have:

   WORD wVersionRequested =MAKEWORD( 1,1);
   WSADATA wsaData;
   long res=WSAStartup( wVersionRequested, &wsaData );
   if(res)
      {
      ShowMessage ( "res so return;" );
      return;
      }

   char ipaddr [] = "172.16.0.102";

   unsigned long inaddr = inet_addr ( ipaddr );

   hostent *myhostent =  gethostbyaddr( (const char FAR *)&inaddr, sizeof ( in_addr ), 0 );

   if ( myhostent ) ShowMessage ( ipaddr + AnsiString ( "\n\n" ) + myhostent->h_name );
   else
      ShowMessage ( ipaddr + AnsiString ( "\n\n" ) + "no myhostent" );

   WSACleanup();

Hans.

Re: gethostbyaddr() does not return any info

#1962

Author: Kris
Date: Tue, 15 May 2007 10:44

14 lines
1376 bytes

Hans Galema wrote:
 > Add some code before and afther what you already have:

Cool. After I changed one little thing in your example code I got it 
working perfectly now. I changed the
gethostbyaddr(..., 0 );
into
gethostbyaddr(..., AF_INET );

Thank you very much for your help.

Regards,

Kris

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