[solved ] binary data to QTcpSocket

[SGaist]

Hi,

Before digging deeper, why do you want/need to read a JPEG like this ?

[S.ANAND]

hi.

Actually i need to transfer jpeg image in a network using QtcpSocket so QTcpSocket::write() function only supports ascii or bytearray . that is the reason to convert to ASCII

[SGaist]

Then, why not simply use QFile's "readAll()":http://qt-project.org/doc/qt-4.8/qiodevice.html#readAll ? It returns you a QByteArray with the data from the file

[S.ANAND]

Hi

That is not working i am getting the same output the second image one.

[mlong]

Don't convert to ASCII. A char* is going to give you trouble the first time it encounters 0x00 (NULL) which will be interpreted as the end of the string. (JPEGs will certainly have a number of NULL characters in them -- I bet the first one you're encountering is at position 5 in your data.) A QByteArray will be sufficient to hold your data. You shouldn't be using a QTextStream at all, also. As SGaist said, QFile::readAll() should get you what you want. However, if you were insistent on using a stream, you'd need to use a QDataStream instead.

How, exactly, are you checking your data?

[S.ANAND]

Thats not working.

I am checking like this
@
QFile file("d:/a.jpg");
file.open(QIODevice::ReadOnly);
ui->textEdit->append(file.readAll());
file.close();
@
It is giving second image output.

edit: please use @ tags around code sections; Andre

[ChrisW67]

Well of course it does. You need to realise that a JPEG file's content is not text and therefore any attempt to treat it is as such (e.g. with QTextStream or QTextEdit, notice the word Text) is doomed to fail. A JPEG binary file will typically have a zero in its fifth byte so you will generally get only four potential characters (byte FF D8 FF E0 in hex) before the string is considered ended. If byte 5 is not zero then the 11th byte will always be zero and you may see a recognisable "JFIF" in the text.

Why don't you take a step back and explain the result you are expecting to achieve.

[Code_ReaQtor]

As ChrisW67 said, JPEG is NOT a text file so QTextEdit won't be able to support it. If you want to show it as text, at least convert it using QByteArray::toHex(). But I don't think we are on the right track then.

[S.ANAND]

@ QFile file("d:/a.jpg");

file.open(QIODevice::ReadOnly);

this->sock = new QTcpSocket;

connect(this->sock,SIGNAL(bytesWritten(qint64)),this,SLOT(q(qint64)));
connect(sock,SIGNAL(connected()),this,SLOT(con()));
connect(sock,SIGNAL(disconnected()),this,SLOT(dis()));

this->sock->connectToHost("192.168.1.2",8080);

this->sock->waitForConnected();

sock->write(file.readAll().data());
sock->waitForBytesWritten(-1);

sock->close();

file.close();
@
This is my code i need to send the image via network using QTcpSocket but the method QTcpSocket::write() will only support char * or bytearray but even if i convert the above image from QString to QByteArry and pass to QTcpSocket and send it is only showing 4 characters in the both cases QByteArray and char *.

Edit: again, use @ tags around code sections please; Andre

[SGaist]

Don't convert anything, just send the byte array created by readAll().

Besides, write(file.readAll().data()) is a bad idea. data() will return a pointer to the data from a temporary QByteArray created by file.readAll(). You don't really know when that byte array will be destroyed.

If you want to show the image on the other end, use a "QImage":http://qt-project.org/doc/qt-4.8/qimage.html + "QLabel":http://qt-project.org/doc/qt-4.8/qlabel.html combo

And please enclose your code with code tags so that it's cleaner to read.

[Code_ReaQtor]

[quote author="S.ANAND" date="1363174874"] QTcpSocket::write() will only support char * or bytearray but even if i convert the above image from QString to QByteArry and pass to QTcpSocket and send it is only showing 4 characters in the both cases QByteArray and char *. [/quote]

It should work... The fact that you are using QTextEdit is NOT correct. QTextEdit only support "Texts".

[S.ANAND]

Ha that's done the trick.
using file.readAll() instead of file.readAll().data()

Thank You SGaist and all others you replied. :)

[S.ANAND]

Yes that is also the mistake i made Code_ReaQtor Thank you .

[SGaist]

You're welcome

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