Server-client receiving and sending problem using QtcpSocket for console application

[Mijaz]

@jsulm I implement your above code its still giving me 0 value on QlcdNumber and in qDebug also.

[Mijaz]

@jsulm from server-side I am not able to send the data in integer I am sending it therefrom QByteArray data; which is socket->write(data); and receiving it on client-side as "\u027" which is not displayed on QlcdNumber. I need the solution for this how I can display it on QlcdNumber.

[jsulm]

@Mijaz This is your code for sending int, right?

data[0] = (uchar) (0x000000ff & current_temp);
data[1] = (uchar) ((0x0000ff00 & current_temp) >> 8);
data[2] = (uchar) ((0x00ff0000 & current_temp) >> 16);
data[3] = (uchar) ((0xff000000 & current_temp) >> 24);

Don't you think you need to do same on the receiver side?
But actually it would be way easier to use https://doc.qt.io/qt-5/qdatastream.html on both sides.

[Mijaz]

@jsulm I did QFile code on both side but I am getting an error QIODevice::read (QFile, "file.dat"): device not open on the receiver side. I am thinking on QTcpSocket how your QFile will work?

[jsulm]

@Mijaz said in Server-client receiving and sending problem using QtcpSocket for console application:

I am thinking on QTcpSocket how your QFile will

Which QFile?!
I never suggested to use any QFile!
QDataStream also works with QByteArray as you can easily see from its documentation...

[KroMignon]

@Mijaz said in Server-client receiving and sending problem using QtcpSocket for console application:

did QFile code on both side but I am getting an error QIODevice::read (QFile, "file.dat"): device not open on the receiver side. I am thinking on QTcpSocket how your QFile will work?

You are going in wrong direction!
Think simple!

Qt has many helper classes.
If I right understand your use case:

• you have an external application which send an integer value per TCP.
• first you said value is send as string, which means for me a text. Decimal value 1 is send as string "1".
• then you said value is send as "raw data", which mean for me a binary. Decimal value 1 is send as 4 bytes ("\x00\x00\x00\x01" or "\x01\x00\x00\x00" depending on endiannes).

To read as text value and convert it back to decimal:

QString str=m_client1->readAll();
bool ok;
int value = str.toInt(&ok);
if(!ok)
  qDebug() << "Could not read integer value";
else
  qDebug() << "Recieved" << value;

To read as binary value and convert it back to decimal:

QByterArray b=m_client1->readAll();
QDataStream stream(b);
// to change byte order (endianess)
// stream.setByteOrder(QDataStream::LittleEndian);
int value;
stream >> value;
if(stream.status() != QDataStream::Ok)
  qDebug() << "Could not read integer value";
else
  qDebug() << "Recieved" << value;

[Mijaz]

@KroMignon Thanks for your excellent approach my value on QlcdNumber displayed successfully but not showing me the actual value current_temp from server-side it is displaying 385875968 instead of 23.

[JonB]

@Mijaz
How should anyone answer this? What is the server actually sending? Where in the stream does it appear? How are you reading it (you might check byte-by-byte initially that you get the right bytes)? How do you convert it to a number (e.g. is your bad number an endian-ness issue)?

[jsulm]

@JonB This is what is sent:

data[0] = (uchar) (0x000000ff & current_temp);
data[1] = (uchar) ((0x0000ff00 & current_temp) >> 8);
data[2] = (uchar) ((0x00ff0000 & current_temp) >> 16);
data[3] = (uchar) ((0xff000000 & current_temp) >> 24);

And as I already wrote before this needs to be considered on the receiver side, but did not hear any feedback...

@Mijaz If you use QDataStream on receiver side you also have to use it on the sender side!

[Mijaz]

@JonB server is actually sending analog temperature sensor value in an integer which is continuously changing via QTcpSocket to client where it is displayed on QlcdNumber.

[Mijaz]

@jsulm Let me try to use QDataStream on the sender side

[JonB]

@jsulm
Ah I see! has anyone checked whether

it is displaying 385875968 instead of 23.

385875968 might be 23 in reverse bytes order (I don't know if it is)?

[Mijaz]

@JonB thanks it's working now.