Sending image in blocks via datastream does not work for other block sizes??

[ganapathi]

Hi

I am sending an image via network in blocks of 20 as shown below:

sender.cpp file****
Sender::Sender(int no)
{
socket = new QUdpSocket( this );
a = 0;
img_block = 0;
block_size = 20;
num = no;

if(num == 1)
image = new QImage("C:/Users/Public/Pictures/Sample Pictures/Desert.jpg" );

if( image->isNull() )
qDebug() << "Failed to open test.jpg" ;
QTimer *timer = new QTimer( this );

timer->isSingleShot();
  QTimer::singleShot(1000, this, SLOT(broadcastLine()) );
  connect( this, SIGNAL(done()), this, SLOT(broadcastLine()) );

}

void Sender::broadcastLine()
{

QByteArray buffer( block_size+3*image->width(), 0 );
QDataStream stream( &buffer, QIODevice::WriteOnly );
stream.setVersion( QDataStream::Qt_5_5 );

stream << (quint16)image->width() << (quint16)image->height();

stream << img_block;

  for( int x=0; x<image->width(); ++x )
  {
            for(int y=block_size*a; y <block_size+(block_size*a);y++)
      {

          if( y < image->height())
          {
           QRgb rgb = image->pixel( x, y );
           stream << (quint8)qRed( rgb ) << (quint8)qGreen( rgb ) << (quint8)qBlue( rgb );
          }
          else
          {
              img_block = y = a = 0;
              img_block = -block_size;
          }
      }
  }


if(num==1)
 socket->writeDatagram( buffer, QHostAddress::Broadcast,9988 );

img_block = img_block + block_size;
a++;

 emit done();

}

The above program works for block_size< 20 but not for 32 which I am interested. I dont have even the slightest idea of whats happening and even how to debug this?

Regards