cannot read correct len from socket

[wysota]

1. sizeof(char) != 4
2. int does not contain decimal digits, it is a binary value ranging from ~ -2^31 to 2^31 (which can hold 10 decimal digits) for a 32 bit integer memory layout
3. reading a value that has not been written cannot end well, can it?
4. you're doing a lot of other errors in your code which completely prove you have no idea what you are doing and just blindly trying to get things working without any understanding what is going on.

Sockets are not magical entities, they do not convert your data, add some artificial data or remove some data -- if you write a sequence of bytes to it, the exact same sequence of bytes will be read by the other end of the communication channel. Don't try to do network programming if you don't understand how it works. Spend two days reading about network programming instead of listening to hints you don't even understand.

[saman_artorious]

Then why are you trying to read them as an integer?

I made a mistake. it is not as chars. it is binary data. So, I need to read the first 4 bytes to get the size of buffer.
The problem is that I cannot simply write an integer to the socket, and read the int 4 bytes in the client.

[wysota]

The problem is that I cannot simply write an integer to the socket, and read the int 4 bytes in the client.

Hmmm... why not?

[saman_artorious]

Then why are you trying to read them as an integer?

I want to read it as binary. appending data length at the beginning with this:

void tcpClient::sendToServer()
{
    QByteArray data;
 
    data.append(5);
    data.append("Saman");
 
    if(clientSocket->write (data) == -1)
    {
        qDebug("write() failed");
    }
}

void tcpClient::sendToServer()
{
    QByteArray data;

    data.append(5);
    data.append("Saman");

    if(clientSocket->write (data) == -1)
    {
        qDebug("write() failed");
    }
}

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in the server, let's read the first 4 bytes, as the size of integer and then read the text.

QByteArray         text;
 
    int length;
 
    clientConnection->read((char*)&length, 4);
 
    qDebug() << length;
 
    text.reserve(length);
 
    clientConnection->read(text.data(), length);
 
    clientConnection->flush();

QByteArray         text;

    int length;

    clientConnection->read((char*)&length, 4);

    qDebug() << length;

    text.reserve(length);

    clientConnection->read(text.data(), length);
    
    clientConnection->flush();

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output:
length read is 1835094789 !

what am I missing?

[Lesiok]

QByteArray::append(5) appends one byte with a value of 5 not integer. Do it in such a way :

clientSocket->write (5);//You are sending int(5) and on other side You can read int
clientSocket->write("Saman");

clientSocket->write (5);//You are sending int(5) and on other side You can read int
clientSocket->write("Saman");

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[saman_artorious]

wrong! that would prompt invalid conversion from int to const char*

[ChrisW67]

QByteArray::append(5) appends one byte with a value of 5 not integer. Do it in such a way :

clientSocket->write (5);//You are sending int(5) and on other side You can read int

clientSocket->write (5);//You are sending int(5) and on other side You can read int

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There's no write(int) function anywhere I can see in the socket/qiodevice interfaces; this won't compile.

[wysota]

I want to read it as binary.

You are always reading it as binary, even if it is textual data. It is just a matter of interpreting the data.

what am I missing?

You are missing a couple of hours of learning about computers, their memory and data layout of different data types.

1835094789d = 0x6D615305 = 0x0553616D (swapped byte order) = "\5Sam" interpreted as text. Does that ring a bell?