Received SMS notification in PDU mode +CMT

+CMT notifies of an unsolicited received message in Protocol Data Unit (PDU) mode. Terminal Equipment (TE) is expected to ack received message with AT+CNMA.

For reference, see 3GPP 27.005 Ch. 3.4.1

The notification is subscribed using the +CNMI command.

Syntax:

+CMT: <alpha>,<length><CR><LF><pdu>

The notification parameters and their defined values are the following:

<alpha>
TP-Originating-Address in string format.
<length>
Number of hexadecimal octets in <pdu>. 1–3 ASCII digits.
<pdu>
Hexadecimal numbers containing two International Reference Alphabet (IRA) characters per octet.

The example returns a notification of a received message "Testing a sms messaging over lte" from +358401234567, Service Center Address +44 888 8888:

+CMT: "+358401234567",28<CR><LF>069144888888F8D4F29C9E769F4161D0BC3D07B5CBF379F89C
       769F416F7B590E62D3CB