Read from QTcpSocket results irregular/wrong data

[wysota]

Accordingly I have all data in my file!

No, you don't. A simple example, just looking at this code:

if (data.contains("=yend")) {
        tcpSocket->close();
    }

if (data.contains("=yend")) {
        tcpSocket->close();
    }

To copy to clipboard, switch view to plain text mode 

What if you first get "=y" and then next time readRead() is emitted, you get "end"? data.contains("=yend") is false in both cases however you have received "=yend".