Suppose you do not want to be dependent on heavy polling to communicate with your AWP (Axeda Wireless Protocol) assets, but you want to keep TCP/IP messaging. You can initiate a shoulder tap from the Axeda Platform, so that an asset that polls infrequently sends a polling message to the Platform after receiving the shoulder tap. The support for shoulder tap messaging in the AWP toolkits and the Axeda Platform allows these wireless assets to avoid polling unless explicitly instructed to poll by the Axeda Platform.
When shoulder tap messaging is enabled, the Axeda Platform sends an SMS or Email message to an asset when the first new message is placed in the shoulder-tap egress table for the asset. If the asset does not respond before another message is placed in the table, the next message is placed in the table without a shoulder tap. Based on a configured schedule, the ShoulderTapRetry task checks the table periodically for assets that have pending messages and a retry count that is less than the configured max retry count for the assets and sends a shoulder tap message to these assets. If an asset responds to the shoulder tap, the Platform downloads the pending messages and removes the asset from the Shoulder Tap table. The messages remain in the table if the asset does not respond.
Notes: If an asset is enabled
for Shoulder Tap messaging and is also configured NOT to poll the Axeda
Platform, then the Ping Rate for the asset is shown as "0" in
the Asset dashboard.
A ping rate of 0 typically means that the asset can never be "Missing."
However, for M2M shoulder-tap assets, the task that checks for missing
assets checks the table of shoulder tap messages to determine if an asset
is Missing. If the number of retries for a shoulder tap message for an
asset has been exhausted and the asset has not responded to the shoulder
tap, the task sets the status of the asset to Missing. If you never
want these assets to show a status of Missing, go to the Missing
Assets page of the Model wizard and select the option, "Don't
consider assets of this model as missing." See also Missing
Assets.
For more information about shoulder tap messaging, refer to Enabling Shoulder Tap Messaging for AWP Assets.