[Qt-interest] large xml over the network - problem

[Jason H]

Why in the world are you doing that?

server side, just do:
out<< xml.toString().toUtf8();

client side:
QBuffer buffer;
in >> buffer;
QDomDocument xml;
xml.setContent(buffer.toString());





----- Original Message ----
From: franki <franki at franki.eu.org>
To: qt-interest at trolltech.com
Sent: Wed, April 27, 2011 10:08:35 AM
Subject: [Qt-interest] large xml over the network - problem

Hi all,

I have client-server application which exchange data using xml's over the net.
With relatively small xml's everything goes fine, but when I try to send big 
ones there is problem with receiving it (not always just from time to time), 
and if I double the size of xml, they are always lost.
Snippet of code on server side:

void NetThread::sendToClient(QDomDocument xml) {
    QByteArray block;
    QDataStream out(&block, QIODevice::ReadWrite);
    out.setVersion(QDataStream::Qt_4_0);
    out << (quint16)0;
    out << xml.toString();
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));
    qDebug() <<" quint size:"<<(quint16)(block.size() - sizeof(quint16))
    qDebug() <<" block size:"<<block.size();
    qDebug() <<" string size:"<<xml.toString().size();
    tcpSocket->write(block);
}

code on client side look's like this (dataSize is quint16):
void NetManager::readData() {
    QDataStream in(socket);
    in.setVersion(QDataStream::Qt_4_0);
    if (dataSize == 0) {
        if (socket->bytesAvailable() < (int)sizeof(quint16))
            return;
        in >> dataSize;
    }
    if(socket->bytesAvailable() < dataSize)
             return;

    QString text;
    in >> text;
    qDebug() << " dataSize:"<<dataSize<<" received:"<<text;
    dataSize=0;
    this->parseData(text);
    if(socket->bytesAvailable())
        this->readData();
}

On the server side, during transmission debug says:
quint size: 3958 
block size: 69496
string size: 34745

On client side when there is successful transmision I got:
NetManager::readData dataSize: 3958  received: "very long_xml_string"

When there is problem with transmission I got:
Debug: NetManager::readData bytes: 3958  received: "" 
Debug: NetManager::parseData parse error 
Debug: NetManager::readData bytes: 61  received: "" 
Debug: NetManager::parseData parse error 
Debug: NetManager::readData bytes: 51  received: "" 
Debug: NetManager::parseData parse error 
Debug: NetManager::readData bytes: 56  received: "" 
Debug: NetManager::parseData parse error 

So in second example the packet length is the same 3958 but the function is 
called 4 times and I'm quite sure that application on server side doesn't 
send anything except for this xml.
So please can someone point me on my errors?

best regards
Marek
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