Client PC is not sending TCP data. (solved)

houmingc

My server is not receiving data from my client.
I used 2 object out (QDatastream) & block (QByteArray) to send TCP data.
Below is my code
Please highlight my mistake.

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            socket.connectToHost(ServerIP,10010);
            qint16 CRC;
            unsigned char TCPdata[5];
            TCPdata[0]=0x20;
            TCPdata[1]=DeviceNum.toInt();
            TCPdata[2]=0x00;
            CRC =ModbusCRC((unsigned char*)TCPdata,3);



            QByteArray block;
            QDataStream out(&block,QIODevice::WriteOnly);
            out.setVersion(QDataStream::Qt_5_0);

            out.device()->seek(0);               // serialize array input.
            out<<0x20<<DeviceNum.toInt()<<0x00<<CRC;  // i presumed this is sending data out via TCP

           socket.writeData(block.data(),block.size());

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SGaist

Hi,

You don't check anywhere that the connection was successful, you should at least check that with waitForConnected or use the connected/error signals

houmingc

I did use connected signals, but it never go into my slots.
I am frustrated and insert all the slots code back into function.

SGaist

Do you also check the error signal ?

houmingc

can you explain why out and block?
is there any link to sample code? i tried but i never really succeed sending the data

ChrisW67

Take a look at the size() at line 18. I guess it will not be the 5 bytes you are expecting but probably something like 14 bytes:
0x20 => 4 byte integer
DeviceNum.toInt() => 4 bytes
0x00 => 4 bytes
CRC => 2 bytes

SGaist

You're not answering the important question: are you checking whether you had an error when trying to connect to your server ?

houmingc

Thanks, this is solved
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psocket = new QTcpSocket(this);
psocket->connectToHost(ServerIP,10010);
if (psocket->waitForConnected(3000)) {
psocket->write(data);
psocket->waitForBytesWritten(1000);
psocket->disconnectFromHost();
}
else
{
qDebug()<<"Not Connected";
}

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