本例所述Delphi程序用于检测网址是否为404，也就是检测网址是否存在，或是否可以打开，针对不同的检查方法，会返回不同的结果。
程序主要代码如下：
unit address;
interfaceuses Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, Psock, NMHttp, StdCtrls, ComCtrls;
type TForm1 = class(TForm) Label1: TLabel;
Edit1: TEdit;
Button1: TButton;
NMHTTP1: TNMHTTP;
StatusBar1: TStatusBar;
procedure Button1Click(Sender: TObject);
procedure NMHTTP1Success(Cmd: CmdType);
procedure NMHTTP1Failure(Cmd: CmdType);
procedure NMHTTP1HostResolved(Sender: TComponent);
procedure NMHTTP1InvalidHost(var Handled: Boolean);
procedure NMHTTP1AuthenticationNeeded(Sender: TObject);
procedure NMHTTP1Connect(Sender: TObject);
procedure NMHTTP1ConnectionFailed(Sender: TObject);
procedure FormActivate(Sender: TObject);
procedure FormClose(Sender: TObject;
var Action: TCloseAction);
procedure NMHTTP1Redirect(var Handled: Boolean);
procedure Edit1KeyDown(Sender: TObject;
var Key: Word;
Shift: TShiftState);
private {
Private declarations }
public {
Public declarations }
end;
var Form1: TForm1;
implementation{
$R *.DFM}
procedure TForm1.Button1Click(Sender: TObject);
var url:string;
begin url:=Edit1.Text;
StatusBar1.simpletext:='正在检验';
NMHTTP1.Head(url);
end;
procedure TForm1.NMHTTP1Success(Cmd: CmdType);
begin case cmd of CmdHEAD: StatusBar1.SimpleText:='网址正确' end;
end;
procedure TForm1.NMHTTP1Failure(Cmd: CmdType);
begin case cmd of CmdHEAD: StatusBar1.SimpleText:='网址不正确，没有这个页面' end;
end;
procedure TForm1.NMHTTP1HostResolved(Sender: TComponent);
begin StatusBar1.SimpleText:='正确解析主机名';
end;
procedure TForm1.NMHTTP1InvalidHost(var Handled: Boolean);
begin StatusBar1.SimpleText:='不能解析主机名';
end;
procedure TForm1.NMHTTP1AuthenticationNeeded(Sender: TObject);
begin StatusBar1.SimpleText:='需要身份验证';
end;
procedure TForm1.NMHTTP1Connect(Sender: TObject);
begin StatusBar1.SimpleText:='连接到主机';
end;
procedure TForm1.NMHTTP1ConnectionFailed(Sender: TObject);
begin StatusBar1.SimpleText:='连接主机失败';
end;
procedure TForm1.FormActivate(Sender: TObject);
begin Edit1.Text:='http://www.';
end;
procedure TForm1.FormClose(Sender: TObject;
var Action: TCloseAction);
begin NMHTTP1.Destroy;
end;
procedure TForm1.NMHTTP1Redirect(var Handled: Boolean);
begin StatusBar1.SimpleText:='重定向到其它页面';
end;
procedure TForm1.Edit1KeyDown(Sender: TObject;
var Key: Word;
Shift: TShiftState);
begin if Key=VK_RETURN then begin StatusBar1.simpletext:='正在检验';
NMHTTP1.Head(Edit1.Text);
end;
end;
end.
