ICMP: TIdIcmpClient;
......
....
procedure TForm1.btnPingClick(Sender: TObject);
var
  i: integer;
begin
  btnPing.Enabled := False; try
    ICMP.Host := Self.ICMP_HOST.Text;
    for i := 1 to 4 do begin
      ICMP.Ping;
      Application.ProcessMessages;
      Sleep(1000);
    end;
  finally btnPing.Enabled := True; end;
end;    // 在 Reply Event 中寫如下 code
procedure TForm1.ICMPReply(ASender: TComponent;
  const ReplyStatus: TReplyStatus);
var
  sTime: string;
begin
  // TODO: check for error on ping reply (ReplyStatus.MsgType?)
  if (ReplyStatus.MsRoundTripTime = 0) then
    sTime := '<1'
  else
    sTime := '=';      lstReplies.Items.Add(Format('%d bytes from %s: icmp_seq=%d ttl=%d time%s%d ms',
    [ReplyStatus.BytesReceived,
    ReplyStatus.FromIpAddress,
    ReplyStatus.SequenceId,
    ReplyStatus.TimeToLive,
    sTime,
    ReplyStatus.MsRoundTripTime]));
end;