how provider sends notification to APNs?

i want to know that if i have a server how do i send push notification to devices through APNs,do 开发者_高级运维i need to register/authenticate my server to APNs.DO i need to pay for sending Push Notification?Any sample code related to this will help better to understand this.

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Go through following doc. It explains in depth the entire system.

Apple's Good Doc About APN Feel free to vote the answer, if you find it helpful.