answers[i].rdata = (unsigned char*)malloc(ntohs(answers[i].resource->data_len));
for(j=0 ; jdata_len) ; j++)
answers[i].rdata[j]=reader[j];
answers[i].rdata[ntohs(answers[i].resource->data_len)] = ‘\0’;

You are allocating a buffer with data_len length, but you access data_len + 1

Use select() before recvfrom()

#include

int CSMTPClient::DiscoverWinsockDNSServers()
{
int iCount = 0;
GUID guid = SVCID_NAMESERVER_UDP;

WSAQUERYSET qs = {0};
qs.dwSize = sizeof(WSAQUERYSET);
qs.dwNameSpace = NS_DNS;
qs.lpServiceClassId = &guid;

HANDLE hLookup;
int nRet = WSALookupServiceBegin(&qs, LUP_RETURN_NAME|LUP_RETURN_ADDR, &hLookup);
if(nRet == SOCKET_ERROR)
{
int iError = WSAGetLastError();
ReportError(_T(“Error obtaining DNS Server information (%d) %s”),
iError, GetWin32ErrorText(iError));
return – 1;
}

// Loop through the services
DWORD dwResultLen = 1024;
unsigned char* pResultBuf = new unsigned char[dwResultLen];

while(TRUE)
{
nRet = WSALookupServiceNext(hLookup,
LUP_RETURN_NAME|LUP_RETURN_ADDR,
&dwResultLen, (WSAQUERYSET*)pResultBuf);
if(nRet == SOCKET_ERROR)
{
// Buffer too small?
if(WSAGetLastError() == WSAEFAULT)
{
delete pResultBuf;
pResultBuf = new unsigned char[dwResultLen];
continue;
}
break;
}

WSAQUERYSET* pqs = (LPWSAQUERYSET)pResultBuf;
CSADDR_INFO* pcsa = pqs->lpcsaBuffer;

// Loop through the CSADDR_INFO array
for(int x = 0; x dwNumberOfCsAddrs; x ++)
{
// Get string equivalent for address
TCHAR strAddrBuf[256] = {_T(”)};
DWORD dwLen = sizeof(strAddrBuf);
nRet = WSAAddressToString(pcsa->RemoteAddr.lpSockaddr,
pcsa->RemoteAddr.iSockaddrLength, NULL, strAddrBuf, &dwLen);
if(nRet == SOCKET_ERROR)
break;

// Remove the port number (‘:#’)
CString strResult = strAddrBuf;
CString strIP = _T(“”);
int i = strResult.Find(_T(‘:’));
if(i == -1)
strIP = strResult;
else
strIP = strResult.Left(i);

// Check for the duplicates before adding it
if(m_slWinsockDNS.Find(strIP) == NULL)
{
m_slWinsockDNS.AddTail(strIP);
iCount ++;
}
pcsa++;
}
}

// Clean up
WSALookupServiceEnd(hLookup);
delete pResultBuf;

return iCount;
}

des = len;
++src; // Ignore ‘.’
} else {
szDns[++des] = szHost[src++];
++szDns[len];
}
}
szDns[++des] = ‘\0’;
}
[/code]

the answer might differ due to a number of reasons. post the output here.

I’ve found the answer.

To do a reverse lookup (PTR) on an IP Address:
1. First reverse the IP address (from say 1.23.45.201 to 201.45.23.1 and append “.in-addr.arpa” to it).
Will now be 201.45.23.1.in-addr.arpa.
2. Call the ChangetoDnsNameFormat() function on it.
3. Add a case in the print answers section for 12 (T_PTR) and handle it the same as T_CNAME
(i.e. look at the answers[i].rdata.c_str() variable).

Happy days.

This is because : 3www6google3com0
look this 3www.7gooogle4gato3com0
The number is the number of characteres after the point. You replace the point with the number of characteres of the text segments.
Sorry for my english!
Enjoy it.

Nice code.
The reversed search is not implemented I think and I can see some interpretation issues when running

Can you fix that?
all the best :)

Yes i already found the link , although thank you

Hi guy, if you pay attention, in the bottom of the article, there´s a link to the linux code: http://www.binarytides.com/blog/dns-query-code-in-c-with-linux-sockets/

Regards.

Regards!

Thanks from Argentina!.