QTcpSocket timeout problem

Hi all!
I have a problem with tcp timeout connection.
/proc/sys/net/ipv4/tcp_keepalive_probes set to 9 and after 9 tcp packet retransmissions without answer ( ack ) nothing happens, connection is lost, server disconnects me, but my app thinks, that everything is ok and even tries to send packets later. It's simply can't recognize that connection is lost.
No signal is emited.
And every minute i send a keep alive notification to server.

Hm,ok.
How i can use qtcpsocket with setsocketopt?
socketDescriptor() always return -1.