Android connection close every double 'pingInterval' seconds

[tankcong]

Hello, I just found this strange problem, my connection receive EVENT_CLOSE every "pingTimeout" time.
For example, server response:

97:0{"sid":"WWJHwp-pcvQh_7bdAE3t","upgrades":["websocket"],"pingInterval":25000,"pingTimeout":60000}

pingInterval is 25s, then my app receives EVENT CLOSE at 50th seconds.
logs:

16:11:40.663 W/System.out: EVENT OPEN
16:12:05.671 I/System.out: ping
16:12:05.730 I/System.out: pong
16:12:30.748 W/System.err: EVENT CLOSE
16:12:35.889 W/System.out: EVENT OPEN
16:13:00.909 I/System.out: ping
16:13:00.960 I/System.out: pong
16:13:25.936 W/System.err: EVENT CLOSE
16:13:31.079 W/System.out: EVENT OPEN
16:13:56.102 I/System.out: ping
16:13:56.162 I/System.out: pong
16:14:21.143 W/System.err: EVENT CLOSE

Seems like ping/pong didn't keep TCP alive.
The version of my library is the latest "0.8.1".