QTcpSocket bytesToWrite permanent increasing

[Milovidov]

Hello all!

I have two devices that are based on blackfin processor and with also compiled by hand via buildroot utility, linux OS. With OS also compiled Qt 4.8.5.
I need to send approximetly 64 kbytes per second via ethernet device with 100mbps interface.
I have problem with slow speed of QTcpSocket. BytesfToWrite increasing permanently, rising up to 30 mb, and then my app recieved segmentation fault, because not exist enouth memory.
The next things that I did for resolving this problem, but this did't has positive result:

1. I measured the speed via netcat utility "such as here":http://deice.daug.net/netcat_speed.html . The Measured speed is 500 kbytes per second, but I need to send only 64 kbytes per second
2. I didn't see dependence from package size - small or big the bytesToWrite increasing in both cases.
3. I set QAbstractSocket::LowDelayOption to 0 or 1, but with no effects.
4. If I calling waitForBytesWritten(-1), the bytesToWrite not growing, but this function work very long time, and I can't call this.
5. Calling flush() has no effects.

As I understand, the problem that QTcpSocket writing slowly when I adding new data. But, is exist any ways for incresing writing speed?

Thank you for attention!