Obtaining DNS Primary and Secondary Address

Posted on 2002-03-30
Last Modified: 2007-11-27
I need to know how to obtain both the primary and secondary DNS addresses from a machine currently connected to the net.

Assume that I will already know if a connection is present, I just need to obtain the DNS numbers and assign them to a String variable in the proper Quad format.
Question by:quantum2
LVL 14

Expert Comment

ID: 6909712
I don't know if this is the proper format, but if you just need to obtain it from the registry, here goes: (Win2K)

Navigate to HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters\Adapters

Loop through the name of the keys to obtain the network interfaces you have (they are enclosed in braces, {}, eg {E0149FCC-34D2-4158-884B-A06F3B6F0F8E})

Let's say you managed to get {E0149FCC-34D2-4158-884B-A06F3B6F0F8E} (that is, HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters\Adapters{E0149FCC-34D2-4158-884B-A06F3B6F0F8E}), remember the key, then navigate to HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters\Interfaces\YourKeyName, eg. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters\Interfaces\{E0149FCC-34D2-4158-884B-A06F3B6F0F8E}

Open the key, then read the value for NameServer. The DNS servers are separated by a comma.

LVL 11

Accepted Solution

shaneholmes earned 100 total points
ID: 6911405
Try this function "GetDNSIP"

 function GetDnsIp : string;
   Output        : TStringList;
   CmdLine       : string;
   CmdLine := GetIpCfgExePath;
   if CmdLine <> '' then
     Output := TStringList.Create;
       case GetBasicOsType of
           if ExecAndGetConsoleOutput (CmdLine, Output) then
             Output.LoadFromFile (GetIpCfg9xOutPath);
           ExecAndGetConsoleOutput (CmdLine, Output);
       if GetDnsIpFromIpCfgOut (Output, DnsIp) then
         Result := DnsIp
         // Attempt to locate via registry
         Result := GetDnsIpFromReg;


function GetDnsIpFromReg : string;
   OpenKey       : HKEY;
   SubKey        : PChar;
   DataSize      : integer;
   Temp          : array [0..2048] of char;
   Result := '';
   SubKey := '';
   Vn := '';
   case GetBasicOsType of
       SubKey := REG_9X_NAMESERVER_PATH;
      Vn := REG_9X_NAMESERVER;
     VER_PLATFORM_WIN32_NT       :
     KEY_READ, OpenKey) = ERROR_SUCCESS then
     DataType := REG_SZ;
     DataSize := SizeOf(Temp);
     if RegQueryValueEx (OpenKey, Vn, nil, @DataType, @Temp,
       @DataSize) = ERROR_SUCCESS then
       Result := string(Temp);
     RegCloseKey (OpenKey);

function GetDnsIpFromIpCfgOut (const Output : TStringList;
   var DnsIp : string) : boolean;
   i     : integer;
   Result := FALSE;
   if Output.Count >= 1 then
     for i := 0 to Output.Count - 1 do
       if Pos(IPCFG_DNS_SERVER_LINE, Output[i]) > 0 then
         DnsIp := Trim(Copy (Output[i], Pos(':', Output[i])+1,
         Result := LooksLikeIp (DnsIp);

Author Comment

ID: 6942364
Thanks a bunch...
Just what I was looking for. I really apprecaite the help.


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