Range Check Error

Hi!


I wrote small program to receive data from RFID reader. Debug and
compilation process was fine but when I started it I received information
that "Range Check Error" occurs.

Is anyone know what could be a reason of this error?

I tried every possible variations and it helped but only a little. I do not
receive this error every time when I start software but problem still
exists.

I'm not a very good Delphi programmer so maybe I made some mistakes in this
code and this is the reason of my problems.


Michal
ps. }Rd!, }Cw, d:GCW, b:04, f:1 and other commands are correct and works
fine when I send them to reader using different software.

Software code:

unit Unit3;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, IdBaseComponent, IdComponent, IdTCPConnection,
IdTCPClient, Math,
  CheckLst;

type
  TForm3 = class(TForm)
    IdTCPClient1: TIdTCPClient;
    Label1: TLabel;
    Label3: TLabel;
    Edit1: TEdit;
    Edit3: TEdit;
    Button1: TButton;
    CheckBox1: TCheckBox;
    Memo1: TMemo;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    procedure Button4Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form3: TForm3;
  aLine, aLine1 : ansistring;
  tr: boolean;
  implementation
{$R *.dfm}

procedure TForm3.Button1Click(Sender: TObject);
begin
if Button1.Caption='Disconnected' then
begin
with IdTCPClient1 do
  begin
    Host:=Edit1.Text;
    Port:=strtoint(Edit3.Text);
    Connect;
    if IdTCPClient1.Connected then
       begin
       CheckBox1.Checked:=true;
       Button1.Caption:='Connected';
       end
       else
       showmessage('No Reader Found!');
  end;
end
else
begin
IdTCPClient1.Disconnect;
Button1.Caption:='Disconnected';
CheckBox1.Checked:=false;
IdTCPClient1.IOHandler.Destroy;
end;
end;


procedure TForm3.Button2Click(Sender: TObject);
var
i: integer;
begin
if IdTCPClient1.Connected then
        begin
             tr:=true;
             IdTCPClient1.IOHandler.WriteBufferOpen;
                if Button4.Enabled=false then
                    begin
                    repeat
                        begin
                        IdTCPClient1.IOHandler.WriteBufferClear;
                        IdTCPClient1.IOHandler.WriteLn('}Rd!');
                        IdTCPClient1.IOHandler.ReadLnSplit(tr,#13#10,20,128);
                        aLine:=IdTCPClient1.IOHandler.ReadLnWait(10);
                        application.processmessages;
                        i:=Length(aline);
                        if i=42 then
                        begin
                        aLine1:=Copy(aLine, 7, 24);
                        Memo1.Lines.Add(aLine1);
                        end
                        else
                        end;
                    until Button3.Enabled=false
                    end
                    else
                    begin
                      tr:=true;
                      IdTCPClient1.IOHandler.WriteLn('}Rd!');
                      IdTCPClient1.IOHandler.ReadLnSplit(tr,#13#10,20,128);
                      aLine:=IdTCPClient1.IOHandler.ReadLn;
                      application.processmessages;
                      i:=Length(aline);
                      if i=42 then
                      begin
                      aLine1:=Copy(aLine, 7, 24);
                      Memo1.Lines.Add(aLine1);
                      end
                      else
                    end;
        end;
end;

procedure TForm3.Button3Click(Sender: TObject);
begin
IdTCPClient1.IOHandler.WriteLn('}Cw, d:GCW, b:04, f:1!');
Button3.Enabled:=False;
Button4.Enabled:=True;
application.processmessages;
end;

procedure TForm3.Button4Click(Sender: TObject);
begin
IdTCPClient1.IOHandler.WriteLn('}Cw, d:GCW, b:07, f:1!');
Button4.Enabled:=false;
Button3.Enabled:=true;
application.processmessages;
end;

end.