delphi WSAAsyncGetHostByName异步取IP地址

同步版本是GetHostByName
异步版本是WSAAsyncGetHOstByName。
它们都是由域名或者主机名返回IP地址。
如果不填写域名，解析出的是本地IP地址。

源代码：
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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls,WinSock;

const
  WM_MYMSG=WM_USER+100;
type
  TMYMSG=record   //自定义的消息结构，也可以不用。
    msg:Word;
    wParam:Word;
    lParam:DWORD;
  end;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    procedure info(var msg:TMessage);message WM_MYMSG;
    { Public declarations }
  end;

var
  Form1: TForm1;
  buf:hostent;
  hwnd1:HWND;

implementation

{$R *.dfm}
{$APPTYPE CONSOLE}

constructor TForm1.Create(AOwner: TComponent);
var
  WSData:TWSAData;
begin
  inherited;
  if WSAStartup(MakeWord(2,0),WSData)<>0 then
    raise Exception.Create('winsock版本错误！');
end;

destructor TForm1.Destroy;
begin
  WSACleanup;
  inherited;
end;

procedure TForm1.Button1Click(Sender: TObject);

begin
  hwnd1:=WSAAsyncGetHostByName(Handle,WM_MYMSG,pchar(edit1.Text),
    pchar(@buf),MAXGETHOSTSTRUCT);
end;

procedure TForm1.info(var msg: TMessage); //自定义的TMYMSG 也可以
begin
  if buf.h_addr=nil then
  begin
    ShowMessage('解析失败！');
    exit;
  end;
  edit3.Text:=buf.h_name;
  edit2.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])]);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  WSACancelAsyncRequest(hwnd1); //中断解析
end;

end.