unit IPC_Handler;

interface

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

type
  TWMMYMessage = record
    Msg: Cardinal; // ( first is the message ID )
    Handle: HWND; // ( this is the wParam, Handle of sender)
    Info: Longint; // ( this is lParam, pointer to our data)
    Handle2: HWND;
    Handle3: HWND;
    PID: LongInt;
    Result: Longint;
  end;

type
   TIPC = class(TForm)
    private

    public
      procedure DefaultHandler(var Message); override;
      procedure WMMYMessage(var Msg: TWMMYMessage);
   end;

Var
    WM_OURMESSAGE: DWORD;

implementation

procedure TIPC.DefaultHandler(var Message);
var
  ee: TWMMYMessage;
begin
  with TMessage(Message) do
  begin
    if (Msg = WM_OURMESSAGE) then
    begin
      ee.Msg := Msg;
      ee.Handle := wParam;
      ee.Info := lParam;
      ee.Handle2 := Application.Handle;
      ee.Handle3 := FindWindow(nil, PChar(Application.Title));
      ee.PID := GetCurrentProcessID;
      // Checking if this message is not from us
      if ee.Handle <> Handle then
        WMMYMessage(ee);
    end
    else
      inherited DefaultHandler(Message);
  end;
end;

procedure TIPC.WMMYMessage(var Msg: TWMMYMessage);
begin
  //Auswertung der Broadcast Message
end;

initialization
  WM_OURMESSAGE := RegisterWindowMessage('Our broadcast message');

end.

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Button1: TButton;
    Label3: TLabel;
    Label4: TLabel;
    Label5: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;


var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  SendMessage(HWND_BROADCAST, IPC_Handler.WM_OURMESSAGE, Handle, Top);
end;

end.