unit local;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    Memo1: TMemo;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

function FindComputer(ComputerName: string):Boolean;

implementation

{$R *.DFM}

function FindComputer(ComputerName: string):Boolean;
var
  WSAData: TWSAData;
  HostEnt: PHostEnt;
begin
  Result :=True;
  WSAStartup(2, WSAData);
  HostEnt := gethostbyname(PChar(ComputerName));
  if HostEnt = nil then Result := False;
  WSACleanup;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if FindComputer(edit1.text)=True then
    Memo1.lines.Add(edit1.text+'在局域網上！')
  else
    Memo1.lines.Add(edit1.text+'不在局域網上！');
end;

end.