The following functions are used for sending and receiving SMS and PDU messages:
•gsmIncomingPDU
Checks for incoming SMS binary PDU messages.
•gsmIncomingSMS
Checks for incoming SMS messages.
•gsmSendFlashSMS
Sends a Flash SMS message
•gsmSendPDU
Sends an SMS message as a binary PDU message.
•gsmSendSMS
Sends an SMS message.
•gsmSetSMSSCN
Sets SMS Service Center Address.
