苹果官方网站消息推送：http://developer.apple.com/library/mac/#documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/ApplePushService/ApplePushService.html
苹果推送服务指南教程：http://www.cnblogs.com/gpwzw/archive/2012/03/31/Apple_Push_Notification_Services_Tutorial_Part_1-2.html