FROM SERVER TO HANDHELD


The process begins when a piece of software detects that there is a new email in your email account. This software can be either the Desktop Redirector or the BlackBerry Enterprise Server. While there are many differences between the Desktop Redirector and the server, in this regard they have the same functionto get the new email message from your account and begin the process of sending it to your handheld.

Processing begins by first removing any attachments that are part of the email message. The attachments are replaced with a stub that will let you know the attachments were there, but not actually sent to the handheld. The stubs also help the Attachment Service to find the attachment if you later want to view the attachment.

Next, the email is broken into chunks. Normally there is only one chunk because most emails are small enough to not need more than one chunk. However, if an email is large enough, the first chunk is separated out. Later, if you make requests for more chunks of an email message, those requests come back to your server and the next chunk is sent out in the same manner as the first.

The last thing that happens is that the message chunk is encrypted. The encryption is done using the encryption key you created in the Desktop Manager when you first set up your handheld.

At this point, the encrypted message chunk leaves your computer and travels over the Internet to something called the BlackBerry Network Operations Center (NOC). The BlackBerry NOC is an important step in the process of delivering your messages, but is also seldom mentioned.

When an encrypted message chunk is sent out, it contains only one piece of information, a PIN number that is the address of the device to receive the chunk. The BlackBerry NOC is essentially a proxy server whose job is to direct the encrypted message chunks to the appropriate carrier. To accomplish this, the BlackBerry NOC has direct connections to each wireless carrier so that this communication happens as fast as possible.

As part of the job of directing the encrypted message chunk to the appropriate carrier, the BlackBerry NOC must also convert the PIN into an address that the carrier can use to deliver the chunk to the handheld. This conversion happens transparently to us because we never have to configure the Desktop Manager with this information. Each time a handheld enters an area with coverage, it communicates with the NOC and tells the NOC what its address is so that the NOC can deliver future messages to the handheld.

Now of course a device is not in coverage areas all the time or is sometimes turned off. When this happens, the NOC saves the encrypted message chunks until the handheld communicates with it again. Once the registration is done, the stored chunks are delivered to the handheld one by one in the order they were received.

Once the encrypted message chunk is on the handheld, there is still one last step that needs to be done. The encrypted message chunk is decrypted using the same encryption key that the Desktop Redirector or BlackBerry Enterprise Server used originally. If there is a problem and the decryption fails, the message chunk is simply discarded. If everything goes well, however, the chunk is processed, the handheld alerts you, and the new message appears in your Message List screen on your handheld. For those of you who like pictures, Figure B.1 shows how all of the components work together to get your email to your handheld.

Figure B.1. How a message gets from your server to your handheld.




Mobile Guide to BlackBerry
Mobile Guide to BlackBerry
ISBN: 0789733439
EAN: 2147483647
Year: 2006
Pages: 146
Authors: Bill Foust

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net