Thanks for the reply!
I apologize for my presumption... you are right!
But I told so, since a friend of mine has the same problem.
We found yesterday a possible workaround of this problem... It seems that connecting the two signals bytesWritten and readyRead, the signal bytesWritten is emitted:

Qt Code: 
  1. socket = new QBuffer(&pckBuffer,this);
  2.     connect(socket,SIGNAL(bytesWritten(qint64)),pCl,SLOT(SendPck(qint64)));
  3.     connect(socket,SIGNAL(readyRead()),this,SLOT(dummy()));
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where dummy can be also a slot that does nothing, just like this:

Qt Code: 
  1. void classname::dummy()
  2. {
  3. }
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With this configuration, the code works for me and also for my friend.
We don't know exactly why, but the code really works!!! Maybe we will check the reason in the Qt source, as suggested by you!

Best Regards,
Alessandro