How was the push notification technology invented, and what is the innovation of Apple's push notification?

1.BB, Nokia and Palm all support push successively. At present, there are three popular push methods.

(1) SMS trigger: Long-term data connection in the 2G era will affect the reliability of telephone access, so Pushmail is triggered by SMS. Push an invisible message to connect the system to the mail server.

(2) Long connection heartbeat query: In the 3G era, the separation of voice and data makes it possible for mobile phones to maintain network connection for a long time. So you can establish a connection, set a certain time interval, and let the mobile phone constantly check the mail of the server.

(3) Long connection IMAP is idle: With the development of the network, the mail push protocol is constantly improving. IMAP began to support idle function. So that the mobile phone does not need to always access the server. When the mobile phone request comes, the mail server can suspend the reply and send it out when there is a new email recently. During this process, the client and the server are always connected.