Question

Possible Duplicate:
Inter-process communication

Using Delphi, is there any possibility that I build two simple programs that communicate and interact with each other, let’s say by clicking a button in the first one the other one displays a message.

Is It Possible?

Answer 1

There are many possebilties for IPC

• Sending window messages
• using Named Pipes
• using TCP-IP / UDP
• shared memory

and so on …

Easiest way would be sending Messages to a window handle found by FindWindow
Named Pipes and TCP-IP should be prefered for extensive communications.

Microdemo:

First Project:

unit Unit2; 

interface

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

type
  TTMiniDemoSender = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  TMiniDemoSender: TTMiniDemoSender;

implementation

{$R *.dfm}
Const
     C_MyMessage=WM_USER + 1234;



procedure TTMiniDemoSender.Button1Click(Sender: TObject);
var
 wnd:HWND;
begin
    wnd := FindWindow('TTMiniDemoReceiver',nil);
  if wnd<>0 then SendMessage(wnd,C_MyMessage,123,456);

end;

end.

Second Project:

unit Unit1;

interface

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

Const
     C_MyMessage=WM_USER + 1234;
type

  TTMiniDemoReceiver = class(TForm)
  private
    { Private-Deklarationen }
    Procedure MyMessage(var MSG:TMessage); message C_MyMessage;
  public
    { Public-Deklarationen }
  end;

var
  TMiniDemoReceiver: TTMiniDemoReceiver;

implementation

{$R *.dfm}

{ TTMiniDemoReceiver }

procedure TTMiniDemoReceiver.MyMessage(var MSG: TMessage);
begin
   Showmessage(IntToStr(MSG.WParam) + '-' + IntToStr(MSG.LParam) );
   msg.Result := -1;
end;

end.

For transferring more information you could use WM_CopyData