unit GetDnsList;
{
采用idsmtp來做郵件特快專遞的一個例子代碼。
部分代碼引用了網上公開的一個例子程序。
我對原例子的dns部分做了改進，現在是直接獲得您當前正在使用的dns地址，無須用戶手工輸入。

chengrong fu 2006-8-2
有任何意見和建議可以給我來信：ufo2003@126.com
}
interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls,
  StdCtrls;


    function GetDnsIp: string;


var
  aDnsList:TStrings;
implementation


Const
  MAX_HOSTNAME_LEN               = 128; { from IPTYPES.H }
  MAX_DOMAIN_NAME_LEN            = 128;
  MAX_SCOPE_ID_LEN               = 256;
  MAX_ADAPTER_NAME_LENGTH        = 256;
  MAX_ADAPTER_DESCRIPTION_LENGTH = 128;
  MAX_ADAPTER_ADDRESS_LENGTH     = 8;

Type
  TIPAddressString = Array[0..4*4-1] of Char;

  PIPAddrString = ^TIPAddrString;
  TIPAddrString = Record
    Next      : PIPAddrString;
    IPAddress : TIPAddressString;
    IPMask    : TIPAddressString;
    Context   : Integer;
  End;

  PFixedInfo = ^TFixedInfo;
  TFixedInfo = Record { FIXED_INFO }
    HostName         : Array[0..MAX_HOSTNAME_LEN+3] of Char;
    DomainName       : Array[0..MAX_DOMAIN_NAME_LEN+3] of Char;
    CurrentDNSServer : PIPAddrString;
    DNSServerList    : TIPAddrString;
    NodeType         : Integer;
    ScopeId          : Array[0..MAX_SCOPE_ID_LEN+3] of Char;
    EnableRouting    : Integer;
    EnableProxy      : Integer;
    EnableDNS        : Integer;
  End;

  PIPAdapterInfo = ^TIPAdapterInfo;
  TIPAdapterInfo = Record { IP_ADAPTER_INFO }
    Next                : PIPAdapterInfo;
    ComboIndex          : Integer;
    AdapterName         : Array[0..MAX_ADAPTER_NAME_LENGTH+3] of Char;
    Description         : Array[0..MAX_ADAPTER_DESCRIPTION_LENGTH+3] of Char;
    AddressLength       : Integer;
    Address             : Array[1..MAX_ADAPTER_ADDRESS_LENGTH] of Byte;
    Index               : Integer;
    _Type               : Integer;
    DHCPEnabled         : Integer;
    CurrentIPAddress    : PIPAddrString;
    IPAddressList       : TIPAddrString;
    GatewayList         : TIPAddrString;
    DHCPServer          : TIPAddrString;
    HaveWINS            : Bool;
    PrimaryWINSServer   : TIPAddrString;
    SecondaryWINSServer : TIPAddrString;
    LeaseObtained       : Integer;
    LeaseExpires        : Integer;
  End;

Function GetNetworkParams(FI : PFixedInfo; Var BufLen : Integer) : Integer;
         StdCall; External 'iphlpapi.dll' Name 'GetNetworkParams';

Function GetAdaptersInfo(AI : PIPAdapterInfo; Var BufLen : Integer) : Integer;
         StdCall; External 'iphlpapi.dll' Name 'GetAdaptersInfo';


function GetDnsIp: string;
Var
  FI   : PFixedInfo;
  Size : Integer;
  Res  : Integer;
  DNS  : PIPAddrString;

begin
  Size := 1024;
  GetMem(FI,Size);
  Res := GetNetworkParams(FI,Size);
  If (Res <> ERROR_SUCCESS) Then Begin
    SetLastError(Res);
    RaiseLastWin32Error;
  End;

    If (FI^.CurrentDNSServer <> nil) Then
    begin
      result:= FI^.CurrentDNSServer^.IPAddress;
    end
    Else result:= '';
   if result= '' then
    begin
     DNS := @FI^.DNSServerList;
     result:= DNS^.IPAddress;
    end;
  FreeMem(FI);
end;

end.