The SMS stack provides two observers. Set SMS Bearer observer and Set Receive Mode observer. Both the observers are created and deleted by the SMS protocol class (SMSPROT).
The Set SMS observer tracks the bearer
settings in the communication database. The set SMS observer changes
the bearer settings in the telephony server, when the SMS bearer settings
are changed in the communication database. The SMS messages can be
sent using the circuit switched and packet switched bearers. If the
observer attempts to change a setting in the telephony server that
is not supported , the observer class returns a KErrNotSupprted to the client applications.
The Set receive mode observer sets the receive mode in the telephony server. The communication database settings of SMS receive mode are monitored by the Set receive mode observer. When there is a change to the receive mode settings in the communication database, the set receive mode observer sets the receive mode in the telephony server. The receive mode settlings are used by the SMS stack to generate the status report message and also to store the messages.