unitdns.pas

Delphi 网络通信协议代码,是多种网络协议的实现代码

unit UnitDNS;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, Winsock;
const
     WM_RESOLVED = WM_USER+100;
Type
    TWMRESOLVED = record
                Msg: WORD;
                wParam:Word;
                lParam:DWORD;
                 end;
type
  TFormMain = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    EditPresentation: TEdit;
    edtHost: TEdit;
    BtnWSAAsyncGetHostByName: TButton;
    BtnWSACancelAsyncRequest: TButton;
    EditResult: TEdit;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure BtnWSAAsyncGetHostByNameClick(Sender: TObject);
    procedure BtnWSACancelAsyncRequestClick(Sender: TObject);
  private
    { Private declarations }
    procedure WMRESOLVED(var Msg:TWMRESOLVED);Message WM_RESOLVED;
  public
    { Public declarations }

  end;

var
  FormMain: TFormMain;
  buf:HOSTENT;
  hAsyncTaskHandle:THandle;
implementation

{$R *.DFM}
procedure TFormMain.WMRESOLVED(var Msg:TWMRESOLVED);
begin
if buf.h_addr=NIL then
   Begin
        EditResult.Text:='Failed to resolve';
        exit;
   end;
EditResult.Text:=Format('%d.%d.%d.%d',
                       [ord( buf.h_addr^[0]),
                       ord(buf.h_addr^[1]),
                       ord(buf.h_addr^[2]),
                       ord(buf.h_addr^[3])]);

     edtHost.Text:=buf.h_name;
end;
procedure TFormMain.FormCreate(Sender: TObject);
Var
   WSAData:TWSAData;
begin
     //initiates use of WS2_32.DLL
     if (WSAStartup(MAKEWORD(2,0),WSAData)<>0) then
        raise Exception.Create('Winsock Version Error');
end;

procedure TFormMain.FormDestroy(Sender: TObject);
begin
     WSACleanUP;
end;
procedure TFormMain.BtnWSAAsyncGetHostByNameClick(Sender: TObject);

begin
     hAsyncTaskHandle:=WSAAsyncGetHostByName(Handle,WM_RESOLVED,pchar(EditPresentation.Text),pchar(@buf),MAXGETHOSTSTRUCT);
end;

procedure TFormMain.BtnWSACancelAsyncRequestClick(Sender: TObject);
begin
     WSACancelAsyncRequest(hAsyncTaskHandle);
end;

end.