Server Push disconenction


I am using the vaadin 7.1.6 in my application.
I have integrated the Server push (manual push support) to update some UI component for Thread.

Once I a launch a heavy operation (fetching data that takes too much times ~ 5-10 min), an exception is raised and it tells me Websocket is disconencted and the progressbar is looping indefinetly.

Please any hint to solve this issue ??