Push Notification (duplicate?)

I've seen other questions here about PNS, in terms of code, but how does the concept work开发者_StackOverflow中文版?do I need to tell my client that they need a server? What goes in the server in terms of configuration/cron or whatever?

Please explain the process. Thanks a ton.

EDIT:

Please explain: Do I need to purchase an SSL certificate, or does Apple issue a "client" or " app" SSL certificate for me?

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Yes, they basically will need a server. The steps go something like:

• User installs application
• Application asks for notification
• Phone talks to APNS, registers for notification for that app and gets a token back
• Application talks to your server to tell it the token
• The phone keeps a connection open to APNS to listen for notifications
• Periodically your server polls APNS for feedback, e.g. that the device has been disabled or the application has deregistered
• When you have a notification, your server tells APNS, and APNS tells the phone, which displays the notification

Note: you download the SSL certificate from Apple provisioning portal.