Changing Local DNS IP

				
//**************************************
// Name: Changing Local DNS IP
// Description:The utility can be used to change the DNS servers of the TCP/IP settings. By default the utility will swap the first two IP address, also you can specify the number as command line argument to set the specified IP as the Primary DNS.
// By: rMatrix
//
// Inputs:Optional, you can specify the number of DNS to set it as Primary DNS.
//
// Side Effects:The utility has been tested on Windows 2000 and Windows XP. It may not work on other platforms.
//
//This code is copyrighted and has// limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=6311&lngWId=3//for details.//**************************************

#include <windows.h>
#include <iostream.h>
#include <stdio.h>
//HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{F7D9F953-70DC-4CED-8145-A7E93D3A953C}
void swap (char* szFirstIp, char* szSecondIp)
{
 char temp [15];
 lstrcpy (temp, szFirstIp);
 lstrcpy (szFirstIp, szSecondIp);
 lstrcpy (szSecondIp, temp);
}
main (int argc, char* argv[])
{
 long lRet;
 TCHAR szKeyValue [128];
 HKEY hKey;
 DWORD dwLen =128;
 char* szKey ="SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\";	//Interfaces\\{1F4380AD-3A8A-4CBC-A692-42223902A720}
 char* szDnsRegisteredAdapters = new char [256] ; 
 
 lstrcpy (szDnsRegisteredAdapters, szKey);
 lstrcat (szDnsRegisteredAdapters, "DnsRegisteredAdapters");
 char* szInterfaceKey = new char [256];
 lstrcpy (szInterfaceKey, szKey);
 lstrcat (szInterfaceKey, "Interfaces\\");
 char* szInterfaceId = new char [128];
 
 PFILETIME lpftLastWriteTime = 0;
 unsigned long ulSize;
 lRet = RegOpenKeyEx (HKEY_LOCAL_MACHINE, szDnsRegisteredAdapters, 0, KEY_ALL_ACCESS, &hKey);
 if (lRet !=0 )
 {
	cout << "Error in accessing the Registry" << endl;
	return 0;
 }
 lRet = RegEnumKeyEx (hKey,0,szInterfaceId, &ulSize,NULL,NULL,NULL, lpftLastWriteTime);
 if (lRet !=0 )
 {
	cout << "Error in enumerating the Registry Keys" << endl;
	return 0;
 }
 RegCloseKey(hKey);
 lstrcat (szInterfaceKey, szInterfaceId);
 
 lRet = RegOpenKeyEx (HKEY_LOCAL_MACHINE, szInterfaceKey, 0, KEY_ALL_ACCESS, &hKey);
 if (lRet !=0 )
 {
	cout << "Error in reading the Registry Keys" << endl;
	return 0;
 }
 lRet = RegQueryValueEx (hKey, TEXT("NameServer"),NULL, NULL, (LPBYTE)szKeyValue, &dwLen);
 if (lRet !=0 )
 {
	cout << "Error in reading the value of Registry Keys" << endl;
	return 0;
 } 
 
 char szIpArray [4][15];
 char *szStringArray = new char [45];
 
 
 char* token;
 
 token = strtok(szKeyValue,","); 
 
 int iTokenCnt = 0;
 
 while (token != NULL)
 {
	lstrcpy(szIpArray [iTokenCnt],token);
	iTokenCnt++;
	 
	token = strtok(NULL,",");
 }
 
 
 if (argc == 1)
 {
	swap (szIpArray [0], szIpArray[1]);
 }
 else
 {
	int k = atoi (argv[1]);
	swap (szIpArray [0], szIpArray[k]);
 }
 
 for (int i = 0; i < iTokenCnt; i++)
 {
	if (i == 0) 
	 lstrcpy (szStringArray, szIpArray [i]);
	else
	{
	 lstrcat (szStringArray, ",");
	 lstrcat (szStringArray, szIpArray [i]);
	}
 }
 lRet = RegSetValueEx (hKey, TEXT("NameServer"), 0, REG_SZ, (LPBYTE)szStringArray, strlen (szStringArray) +1);
 if (lRet !=0 )
 {
	cout << "Unable to write the modifications in the Registry." << endl;
	return 0;
 }
 RegCloseKey(hKey); 
 return 0;
}