application disconnects after few seconds

i am using openfire 3.9 and strophe at client side , i am using HTTP-BINING too.

now the issues is after i connect with a server and leave my application as it is , it disconnects after few seconds , like around 40 sec after it disconnects

so is there any way in openfire to keep the connection alive for a longer period of time ?  do i need to set any system properties for the same ?