The doc says its only for sending, but I need to receive it:

QtTelnet::EndOfFile 7 Sends the END OF FILE control message.
sendControl(QtTelnet::EndOfFile)

I tried to check the underlying socket, but that only gave me an empty buffer (supposedly already flushed inside of QtTelnet):

class TelnetClientDialog
{
QtTelnet t; // logged in etc

TelnetClientDialog()
{
connect( t, ..message.., this, ..slotReceiveMessage.. );
}

void slotReceiveMessage(const QString &msg)
{
QByteArray data = t->socket()->readAll();
qDebug() << "bytesArray=" << data;
qDebug() << "bytesArray eof=" << data.indexOf( '\0' );
}
};

data is "" and indexOf says -1