The set command sends a new message ACK in text mode. This command can be used only when the modem is activated.
If the User Equipment (UE) does not get an acknowledgement within the required time (network timeout), it should respond as specified in 3GPP TS 24.011 and the UE/Terminal Adapter (TA) shall automatically disable routing to Terminal Equipment (TE) by setting both <mt> and <ds> values of +CNMI to zero, that is, the SMS client gets unregistered.
Syntax:
+CNMA
The following command example sends a new message ACK in text mode:
AT+CNMA
OK