Så här fungerar Exchange push:
"The versions of EAS supported in Exchange Server 2003 Service Pack 2 and Exchange 2007 use a significantly different technology called Direct Push (Figure 1). Direct Push, which is supported by Windows Mobile 5 with MSFP (or later) and a number of EAS licensees, uses a client-created HTTPS connection to the server. The mobile device creates a connection and keeps it open for a duration known as the heartbeat interval, sending an initial synchronization request when the connection is opened. The server will then take several actions:
• When the device makes an initial connection, it may send the heartbeat interval and a list of subscribed folders to the server. If the server receives these items, it stores them in an XML file in the user’s mailbox; if it doesn’t receive them, it retrieves them from the mailbox.
• The server will ask the mailbox server for notification of changes to items in the list of subscribed folders from the device.
• If there are unsynchronized changes on the server, the server immediately returns a status code that tells the client that changes are available; the client will then initiate synchronization and pull the new changes.
• If there are no changes since the last synchronization, the server does nothing.
• When the heartbeat interval expires, the server sends a notification to the client, which can then re-establish the connection."
Mobilen skickar alltså en signal till servern då och då (hur ofta har jag inte koll på, men det är inte speciellt ofta, och absolut inte konstant!) för att visa att den fortfarande lever. Om det finns nya mail skickar servern ett meddelande till mobilen som säger åt den att hämta mail.
