Verbindungsproblem mit Firebird

[Hansi]

Hey,

Hier der Code:

Delphi-Quellcode:

unit Unit_Hauptformular;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Menus, IniFiles, ZConnection;

const
  INICONNECTIONDATA = 'Connectiondata';
  INI_Hostname = 'Hostname';
  INI_Port = 'Port';
  INI_User = 'User';
  INI_Password = 'Password';
  INI_Database = 'Database';

type
  TForm_Hauptformular = class(TForm)
    MainMenu1: TMainMenu;
    Datei1: TMenuItem;
    Beenden1: TMenuItem;
    Hilfe1: TMenuItem;
    Info1: TMenuItem;
    ZConnection1: TZConnection;
    procedure FormCreate(Sender: TObject);
    procedure Beenden1Click(Sender: TObject);
  private
    IniFile :TIniFile;
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form_Hauptformular: TForm_Hauptformular;

implementation

{$R *.dfm}


procedure TForm_Hauptformular.FormCreate(Sender: TObject);
var
  a,b,c,d,e:String;
begin
  IniFile := TIniFile.Create(ChangeFileExt(Application.ExeName, '.ini'));
  with IniFile do
  begin
    a := ReadString(INICONNECTIONDATA, INI_Hostname, 'localhost');
    b := ReadString(INICONNECTIONDATA, INI_Port, '3306');
    c := ReadString(INICONNECTIONDATA, INI_User, 'SYSDBA');
    d := ReadString(INICONNECTIONDATA, INI_Password, 'masterkey');
    e := ReadString(INICONNECTIONDATA, INI_Database, 'AP_v4');
  end;
    IniFile.Free;
  try
    with ZConnection1 do
      begin
        HostName  := INI_Hostname;
        Port      := StrToInt(INI_Port);
        User      := INI_User;
        Password  := INI_Password;
        Database  := INI_Database;
        Connect;
      end;
    ShowMessage('Verbindung erfolgreich!');
  except
    ShowMessage('Verbindung fehlgeschlagen!');
  end;
end;

procedure TForm_Hauptformular.Beenden1Click(Sender: TObject);
begin
  close;
end;

end.

Immer kommt die Fehlermeldung "Verbindung fehlgeschlagen"!

Kann mir jemand helfen?