push 原理

Iphone push 原理
http://slj.me/2010/02/iphone-push-notification/
服务器和手机上跑着的都是基于Jabber/XMPP协议的类IM程序。手机加服务器为好友，而服务器加所有使用Push的手机为好友(数量一定非常惊人，所以稳定性是问题。这应该也是Push Notification反复跳票的原因。)。
http://www.ifanr.com/3371


iphone push的文章：
http://mobiforge.com/developing/story/programming-apple-push-notification-services
http://blog.boxedice.com/2009/07/10/how-to-build-an-apple-push-notification-provider-server-tutorial/
http://blog.boxedice.com/2010/06/05/how-to-renew-your-apple-push-notification-push-ssl-certificate/
http://www.iphone-geek.cn/%E7%BC%96%E7%A8%8B/%E6%80%8E%E6%A0%B7%E7%BC%96%E5%86%99apple-push-notification%E6%9C%8D%E5%8A%A1%E5%99%A8


iphone push的重点：
1、By requesting the device token and passing it to the provider every time your application launches, you help
to ensure that the provider has the current token for the device. If a user restores a backup to a device other
than the one that the backup was created for (for example, the user migrates data to a new device), he or
she must launch the application at least once for it to receive notifications again. If the user restores backup
data to a new device or reinstalls the operating system, the device token changes. Moreover, never cache a
device token and give that to your provider; always get the token from the system whenever you need it. If
your application has previously registered, calling registerForRemoteNotificationTypes: results in
iOS passing the device token to the delegate immediately without incurring additional overhead.
2、Important: Because delivery is not guaranteed, you should not depend on the remote-notifications facility
for delivering critical data to an application via the payload. And never include sensitive data in the payload.
You should use it only to notify the user that new data is available.