Why QTcpSocket read(len) has prefix ?

sonichy

connect(tcpSocket, SIGNAL(readyRead()), this, SLOT(readMessage()));

void MainWindow::readMessage()
{ 
    qint64 len = tcpSocket->bytesAvailable();    
    qDebug() << "receive(" << len << ")";
    QByteArray BA = tcpSocket->read(len);
    qDebug() << "ByteArray(" << BA << ")";
}

old.htm (file name)
ByteArray( "\x00\x07old.htm" )

file content
ByteArray( "\x00\x00\x00\x00\x00\x00\b\xA2<html>\n......" )

jsulm

@sonichy Please explain what you mean. What prefix?
Also, don't forget that the data you're sending can arrive in several packets. That means: tcpSocket->read(len) does not necessarily return the whole package you sent. You need to accumulate data in a QByteArray until you notice that you got whole package.

sierdzio

@jsulm said in Why QTcpSocket read(len) has prefix ?:

@sonichy Please explain what you mean. What prefix?

He (claims he) is sending old.htm but receiving \x00\x07old.htm.

VRonin

How are you writing those? \x00\x07 is the size of the subsequent string as a 16bit integer. would make sense to me as a header written by a structured serialiser

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Why QTcpSocket read(len) has prefix ?