[Qt-interest] QTcpSocket & QDataStream

[pmqt71]

Both client and server run on my laptop. Same Qt version, compiler...

the setVersion is called in both sides on QDataStream

*setVersion(QDataStream::Qt_4_0);*


2011/2/5 Andreas Pakulat <apaku at gmx.de>

>  On 05.02.11 11:02:15, pmqt71 wrote:
> > Hi,
> >
> > I'm sending data from a client to a server using QTcpSocket just as
> > described in the fortune example. But when the server reads, it finds the
> > data shifted by 4 bytes (in wich I find the length of the QByteArray used
> in
> > the client side).
> >
> > Something similar happens in the following example. QByteArray::data (or
> > constData) is the same used by QTcpSocket to write a QByteArray.
> >
> >
> > *QByteArray ba;*
> > *char *ss = NULL;*
> > * *
> > *QDataStream ds(&ba, QIODevice::WriteOnly);*
> > *ds << "hello";*
> > *ss = ba.data();   //ss is empty*
> > *ss += 4;            //ss contains "hello"*
> >
> > The first 4 bytes seems to contain the length of ba: 0,0,0,6
> >
> > If I don't use QDataStream I have no extra bytes:
> >  *QByteArray ba;*
> > *char *ss = NULL;*
> > * *
> > *ba.append("hello");*
> > *ss = ba.data();   //ss contains "hello"*
> >
> >
> > I should skip the first 4 bytes before reading my data (that already
> contain
> > a length), but I don't find the same instruction in the fortune example.
> > Where is the problem in my code?
>
> Are you using the same qt version to read the content as you use for
> writing? Or maybe you don't use Qt at all for reading? QDataStream has
> an internal data format which is being used to store the data you put
> into it into a list of bytes. This format is specific to QDataStream and
> may change between different Qt versions, hence you can specify which
> QDataStream format you want to use with the aproriate setter. So make
> sure that both sides use QDataStream to read the data and they use the
> same data-format version.
>
> Andreas
>
> --
> Beware of a tall blond man with one black shoe.
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