javax.naming.CommunicationException in java code

Hi
i have written a utility, where we fetch Group Name and Users details from Active Directory. Normally utility works fine and fetch data in 7-8 minutes. From last few days, it is geting stuck. The error i am gettinf in logs is

"javax.naming.CommunicationException: connection closed [Root exception is java.io.IOException: connection closed".

Please help.

Have you check the connection to the directory service? Is it running? Or whether you have a network problem that not enable you to connect to the directory server?

My code logic is as below:
It is fetching groups from AD and for each group it fetch member details.
Now also it is fetching groups but while fetching members it get stuck.