QTcpSocket can't read all bytes

[Qiieha]

Hi

a server sends 162076 bytes to the client. The client reads the QTcpSocket and gets only 16384 bytes back and the program crashes.

What's the best way to read all data?

QByteArray byteblock = tcpsocket->read();
QDataStream stream(&byteblock, QIODevice::ReadOnly);
QString str;
stream >> str;
qDebug() << "received:" << str;

QByteArray byteblock = tcpsocket->read();
QDataStream stream(&byteblock, QIODevice::ReadOnly);
QString str;
stream >> str;
qDebug() << "received:" << str;

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Debug output is: received ""

thank u!

[wysota]

No, this is definitely wrong. Why are you using QDataStream?

[Qiieha]

thank u for your reply!
I saw this solution in some examples...

what should I use instead?
can u suggest something

[wysota]

Instead don't use QDataStream if you don't know what it does

[Qiieha]

what should I use?

[wysota]

You can use QTcpSocket, that you are already using. But basically everything depends on what the server is sending.

[Qiieha]

the server writes a QByteArray to the socket:

tcpsocket->write(bytearray);

tcpsocket->write(bytearray);

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and the bytearray has a size of 162076

[wysota]

Then read a byte array. But remember TCP is a stream protocol, don't expect to receive all data in one piece (that's the main reason why your datastream code was incorrect).

[Qiieha]

I try it like this:

void Interface::readyReadSlot()
{
    qDebug() << "readyReadSlot()";
    QByteArray byteblock;
    while (!tcpsocket->atEnd()) {
        QByteArray data = tcpsocket->read(100);
        byteblock += data;
    }
    QDataStream stream(&byteblock, QIODevice::ReadOnly);
    QString string;
    stream >> string;
    qDebug() << "received:" << in_string;
}

void Interface::readyReadSlot()
{
    qDebug() << "readyReadSlot()";
    QByteArray byteblock;
    while (!tcpsocket->atEnd()) {
        QByteArray data = tcpsocket->read(100);
        byteblock += data;
    }
    QDataStream stream(&byteblock, QIODevice::ReadOnly);
    QString string;
    stream >> string;
    qDebug() << "received:" << in_string;
}

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if the server sends a too long bytearray the Debug-Output is received " ", otherwise it's correct.
What's wrong?

[wysota]

I think you really need to learn how TCP works. There is no concept of a socket being "at end". Your approach is simply incorrect. When data arrives, append it to a buffer and when you have all the data you expect then make use of it. Of course you need to know how much data to expect. Such information needs to be encoded in the data stream (for instance you can use the newline character as a request delimiter or you can prepend the size of the record you are sending to the stream).

[Qiieha]

the datastream consists of XML, so I could use the </end> tag as information, couldn't I?