[SOLVED]Need Help:structure over socket

[KA51O]

[quote author="qxoz" date="1362637580"]Here is the implementation of idea:
@void transmit()
{
structName structCall;
structCall.varint = 5;
structCall.varchar [10] ='AaBbCcDdEeFf';

QByteArray sendArray;
QDataStream out(&sendArray,QIODevice::WriteOnly);
out.setVersion(QDataStream::Qt_4_8);
out << request;
socket->write(sendArray);

}@
[/quote]
I think in line 10 of the transmit function its supposed to be out << structCall ?

[qxoz]

Yes you right :). I missed it.
Fixed now.
Thanks KA51O.

[Qt Nico]

This is exactly what I am looking for.

But I noticed, when I try to send the data.

for example:

I give varint with a value of 5 on my "transmit function"
@
structCall.varint = 5;
socket->write(sendArray);
qDebug() << "DATA" << sendArray;
@

and my "Application Output" reported:
"DATA 00000005"

And it actually sends "00000005" data instead of "05" data only over the socket.
so, what should I do to eliminate the first "000000" and enable me to send only "05".

thanks qxoz, you save a lot of time of me.

[andre]

I don't quite get the roundtrip through QByteArray, to be honest. QStreamWriter can operate directly on the socket...

Anyway, I will assume your implementation of the streaming operator for your structName is still like this:
@
QDataStream &operator <<(QDataStream &out,const structName &dataStruct)
{
out << dataStruct.varint;
out.writeRawData ( dataStruct.varchar, 10 );
return out;
}
@

Here, you first output the int. You are using a plain int, but I'd recommend to always use variables with a guaranteed size for these purposes. int normally is the same as qint32. So, you have a 32 bits (four bytes) value. You will need to send all of these bytes in the stream. If your value has a smaller range, you should use a smaller data type like quint16 or qint8. Otherwise, on the receiving side, there is no way to know how to read in the data again. Note that this is binary data, not text that you are seeing.

[qxoz]

[quote author="Andre" date="1362650288"]I don't quite get the roundtrip through QByteArray, to be honest. QStreamWriter can operate directly on the socket...
[/quote]
This failings of my knowledge :)

[andre]

/teacher mode...

QDataStream is a class that is meant to operate on a [[doc:QIODevice]]. The socket is such an IO device. If you use it on a QByteArray, it actually creates a [[doc:QBuffer]] in the background. QBuffer is a class that provides a QIODevice interface on a QByteArray.

[Qt Nico]

Sir Andre, your recommendation actually works with int. But I still having a problem with variable type like QbyteArray and char.

[qxoz]

Thank you Andre.
Qt Nico@what problem with char do you have?

[Qt Nico]

Problem is now solved. Thanks Sir Andre and qxoz. thanks to everyone.

[andre]

Note that I'd recommend against sending raw data in the form of a @char[10]@ or something like that. I'd just use a QByteArray instead.

[vahidnateghi]

@struct your_structure
{
//variables
},test@

When you want to send the structure:
@char * sendPack = (char *)&test;
writeDatagram((const char *)sendPack,sizeof(your_structure),destIP,destPORT);@

When you want to receive the packet:
@char recPack[sizeof(your_structure)];
readDatagram((char *)&inPack, sizeof(your_structure),senderIP, senderPort);
your_structure * inp = new your_structure();
inp = (your_structure *)inPack;@

[andre]

[quote author="vahidnateghi" date="1383463791"]@struct your_structure
{
//variables
},test@

When you want to send the structure:
@char * sendPack = (char *)&test;
writeDatagram((const char *)sendPack,sizeof(your_structure),destIP,destPORT);@

When you want to receive the packet:
@char recPack[sizeof(your_structure)];
readDatagram((char *)&inPack, sizeof(your_structure),senderIP, senderPort);
your_structure * inp = new your_structure();
inp = (your_structure *)inPack;@[/quote]

That won't work if you're on different architectures, like trying to communicate between a 32 bits and a 64 bits version of your application, to name just one possible problem with this approach. My advise: never, ever do it this way.

[vahidnateghi]

[quote author="Andre" date="1383491720"]

That won't work if you're on different architectures, like trying to communicate between a 32 bits and a 64 bits version of your application, to name just one possible problem with this approach. My advise: never, ever do it this way.
[/quote]

Yes,you're right, when I used it and it worked, it was between two machines with the same architecture...