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Short Message Service

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An application can load the Subscriber Identity Module (SIM) application programming interface (API) DLL to access the SMS services present on digital wireless devices. Smartphone and Pocket PC support several types of SMS messages, including text, notification, Wireless Datagram Protocol (WDP), and cellular broadcast.

SMS Proxy and SMS Router, which originally received the SMS message, are the two layers that make up the SMS component for Smartphone and Pocket PC. The SMS Proxy resides in the process space of its host application and is used by applications as an API layer to access the SMS Router. The SMS Router is in the process space of Device.exe and contains most of the functionality for the features exposed by the SMS Proxy layer. DeviceIOControl is the means of communication between the two layers. The layer below the SMS Router is the radio interface layer (RIL).

The following graphic shows the SMS architecture.

The SMS Router uses the following libraries:

  • SMS Providers   Multiple providers in one or more DLLs
  • SMS Router Toolkit   gsm.dll
  • SMS Store   CoreDrv.dll

The SMS Router uses SMS Providers to deliver, encode, decode, and receive SMS messages. SMS Providers correspond to SMS message types that are sent or received. An application can be registered to an SMS Provider, so that when an incoming SMS message matches the provider that it is registered with, the application can be invoked. Only one application can be registered to read messages from each provider. However, multiple applications can send SMS messages through a single SMS Provider.

The SMS Router has an SMS Store as a generic buffer or backup to keep copies of SMS messages that have been received. It stores SMS messages while they are being processed by the SMS Providers. The SMS Store can also be used in the event of an application failure or device shutdown. SMS messages are deleted from just the SMS Store only after an application has finished reading it.

See Also

SMS Router | Processing Messages

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