Working with background in ios

Working with background in ios

I have developed socket.IO for iOS Application . When app is running, app
can send and receive http socket data without any problem .
All i want to do , I want to get messages when app get in background.
I think appdelegate.h 's delegate method :
- (void)applicationDidEnterBackground:(UIApplication *)application
works for it . But how can i implement my function in that scope ?