Correct way to read TCP packet :socket->readAll()?

ganapathi

Hi

Client is sending an image(768 by 1024) by breaking them into stripes of 768 by 20 ie image block size is 20 using a TCP socket:

Client_Image::Client_Image()
{

socket = new QTcpSocket(this);
a = 0;
img_block = 0;
block_size = 20;

socket->connectToHost("127.0.0.1",1234);

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

     if( image->isNull() )
    qDebug() << )"Failed to open test.jpg" ;
    else
     qDebug() << "Opened the test.jpg" ;

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

}

void Client_Image::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
          {
              y = a = 0;
              img_block = -block_size;
          }
      }
  }


socket->write(buffer);
qDebug() << buffer.size() << "buffer size";

 socket->waitForBytesWritten(10);
 socket->flush();
 img_block = img_block + block_size;  
 a++;

 emit done();

}

I receive the image at the server:The corresponding code is shown below.

void ClientSocket::readyRead()
{

     ********** **  QByteArray buffer =  socket->readAll();**************
       qDebug() << "socket read data\n";


     QDataStream stream( buffer );
     stream.setVersion( QDataStream::Qt_5_5 );
     quint16 width, height, y;
     stream >> height >> width >> y;
    qDebug() << "crl1" << width << height;

     qDebug() << "socket read data 1\n";


     if( !image )
         image = new QImage( width, height, QImage::Format_RGB32 );
     else if( image->width() != width || image->height() != height )
     {
         delete image;
         image = new QImage( width, height, QImage::Format_RGB32 );
     }

     qDebug() << "socket read data 2\n";

     for( int x=0; x<width; ++x ) {
         for( int z=y;z<y+block_size;z++){
         quint8 red, green, blue;
         stream >> red >> green >> blue;
         image->setPixel( x, z, qRgb( red, green, blue ) );
         }
     }

 qDebug() << "socket read data 3\n";

 setPixmap( QPixmap::fromImage( *image ) );

 resize( image->size() );

 this->show();

}

I dont know the correct way of reading the incoming TCP packet.
QByteArray buffer = socket->readAll();

Should i communicate the block size of image and then read only those bytes at the server. How to do it? I have no idea.

Hope some one will help me out.

Warm Regards

SGaist

Hi and welcome to devnet,

Take a look at the "Fortune Server Example" in Qt's documentation, you'll see how to send data through QTcpSocket with QDataStream.

On a side note, you don't need to allocate QImage on the heap,