here are many situation when you need to allow for two applications to communicate. If you do not want to mess with TCP and sockets communication (because both applications are running on the same machine), you can *simply* send (and properly receive) a special Windows message: WM_COPYDATA.

type  TCopyDataStruct = packed record    dwData : DWORD;    // up to 32 bits of data to be passed to the receiving application    cbData : DWORD;    // the size, in bytes, of the data pointed to by the lpData member    lpData : Pointer;    // Points to data to be passed to the receiving application. This member can be nil.  end;

procedure TSenderMainForm.SendString( );var  stringToSend : string;  copyDataStruct : TCopyDataStruct;begin  stringToSend := ‘About Delphi Programming‘;  copyDataStruct.dwData := 0; // use it to identify the message contents  copyDataStruct.cbData := 1 + Length( stringToSend );  copyDataStruct.lpData := PChar( stringToSend );  SendData( copyDataStruct );end;

procedure TSenderMainForm.SendData( const copyDataStruct : TCopyDataStruct );var  receiverHandle : THandle;  res : integer;begin  receiverHandle := FindWindow( PChar( ‘TReceiverMainForm‘ ),    PChar( ‘ReceiverMainForm‘ ) );  if receiverHandle = 0 then  begin    ShowMessage( ‘CopyData Receiver NOT found!‘ );    Exit;  end;  res := SendMessage( receiverHandle, WM_COPYDATA, integer( Handle ),    integer( @copyDataStruct ) );end;

type  TReceiverMainForm = class( TForm )  private    procedure WMCopyData( var Msg : TWMCopyData ); message WM_COPYDATA;  end;type  // The TWMCopyData record is declared as:  TWMCopyData = packed record    Msg : Cardinal;    From : HWND; // Handle of the Window that passed the data    CopyDataStruct : PCopyDataStruct; // data passed    Result : Longint; // Use it to send a value back to the "Sender"  end;implementationprocedure TReceiverMainForm.WMCopyData( var Msg : TWMCopyData );var  s : string;begin  s := PChar( Msg.CopyDataStruct.lpData );  // Send something back msg.Result := 2006;end;

procedure TSenderMainForm.SendImage( );var  ms : TMemoryStream;  bmp : TBitmap;  copyDataStruct : TCopyDataStruct;begin  ms := TMemoryStream.Create;  try    bmp := self.GetFormImage;    try      bmp.SaveToStream( ms );    finally      bmp.Free;    end;
    copyDataStruct.dwData := Integer( cdtImage ); // identify the data    copyDataStruct.cbData := ms.Size;    copyDataStruct.lpData := ms.Memory;    SendData( copyDataStruct );
  finally    ms.Free;  end;end;// And how to receive it:procedure TReceiverMainForm.HandleCopyDataImage( copyDataStruct : PCopyDataStruct );var  ms : TMemoryStream;begin  ms := TMemoryStream.Create;  try    ms.Write( copyDataStruct.lpData^, copyDataStruct.cbData );    ms.Position := 0;    receivedImage.Picture.Bitmap.LoadFromStream( ms );  finally    ms.Free;  end;end;