26. Reading SMS Messages from a Message Storage Area Using AT Commands (AT+CMGR, AT+CMGL)

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To enable a computer / PC to read SMS messages from a message storage area, the GSM/GPRS modem or mobile phone has to support either of the AT commands +CMGR (command name in text: Read Messages) and +CMGL (command name in text: List Messages). The +CMGR AT command is used to read an SMS message at a certain location of the message storage area, while the +CMGL AT command is used to read SMS messages that have a certain status from the message storage area. The status can be "received unread", "received read", "stored unsent", "stored sent", etc. The +CMGL AT command also allows you to retrieve all SMS messages stored in the message storage area.

Following is an example for illustrating the difference between +CMGR and +CMGL. Suppose you want to use your computer / PC to read a text message from the message storage area and you know the index at which the SMS text message is located. In this case, you should use the +CMGR AT command. Here is the command line to be typed (assume the SMS text message is stored at index 3):

AT+CMGR=3

The GSM/GPRS modem or mobile phone should return something like this:

+CMGR: "REC READ","+85291234567",,"07/02/18,00:12:05+32"
Hello, welcome to our SMS tutorial.

OK

Suppose you are now in another situation. You want to use your computer / PC to retrieve all inbound SMS messages that have not been read before. In this case, you should use the +CMGL AT command. In SMS text mode, the command line to be used should be:

AT+CMGL="REC UNREAD"

The GSM/GPRS modem or mobile phone should return something like this:

+CMGL: 1,"REC UNREAD","+85291234567",,"07/02/18,00:05:10+32"
Reading text messages is easy.
+CMGL: 2,"REC UNREAD","+85291234567",,"07/02/18,00:07:22+32"
A simple demo of SMS text messaging.

OK

The +CMGL AT command can also be used to read all SMS messages stored in the message storage area. To do so in SMS text mode, the command line should be:

AT+CMGL="ALL"

This time the response of the GSM/GPRS modem or mobile phone should be something like this:

+CMGL: 1,"REC READ","+85291234567",,"07/02/18,00:05:10+32"
Reading text messages is easy.
+CMGL: 2,"REC READ","+85291234567",,"07/02/18,00:07:22+32"
A simple demo of SMS text messaging.
+CMGL: 3,"REC READ","+85291234567",,"07/02/18,00:12:05+32"
Hello, welcome to our SMS tutorial.

OK

As you can see above, the +CMGR AT command can only be used to read one SMS message at a time, while the +CMGL AT command can be used to read multiple SMS messages at a time.

Another difference between the AT commands +CMGR and +CMGL is that +CMGR can be used to retrieve more message details than +CMGL when the GSM/GPRS modem or mobile phone is operating in SMS text mode. Here are the message details that can be retrieved by the +CMGR AT command in SMS text mode:

• Status of the SMS message ("received unread", "received read", "stored unsent", "stored sent", etc).

• Originator/recipient phone number stored in the SMS message header and the type of the phone number.

• Text associated to the originator/recipient phone number in the phonebook.

• Time and date at which the SMS message arrived at the SMSC (available to incoming SMS messages only).

• The first octet (1 octet = 8 bits) of the TPDU (Transport Protocol Data Unit) of the SMS message.

• The protocol identifier value in the TPDU of the SMS message.

• The data coding scheme value in the TPDU of the SMS message.

• SMSC number stored with the SMS message and the type of the SMSC number.

• Validity period of the SMS message (available to outgoing SMS messages only).

• Body of the SMS message and its length.

Here are the message details that can be retrieved by the +CMGL AT command in SMS text mode:

• The index specifying the location of the SMS message in the message storage area.

• Status of the SMS message ("received unread", "received read", "stored unsent", "stored sent", etc).

• Originator/recipient phone number stored in the SMS message header and the type of the phone number.

• Text associated to the originator/recipient phone number in the phonebook.

• Time and date at which the SMS message arrived at the SMSC (available to incoming SMS messages only).

• Body of the SMS message and its length.

If you compare the above two lists, you will find that the following message details can only be retrieved by the +CMGR AT command but not the +CMGL AT command:

• The first octet of the TPDU of the SMS message.

• The protocol identifier value in the TPDU of the SMS message.

• The data coding scheme value in the TPDU of the SMS message.

• SMSC number stored with the SMS message and the type of the SMSC number.

• Validity period of the SMS message (available to outgoing SMS messages only).

Note: If the GSM/GPRS modem or mobile phone is operating in SMS PDU mode, the message details that can be retrieved by +CMGR and +CMGL are the same.

26.1. Comparison Table of the AT Commands +CMGR and +CMGL

The comparison table below summarizes the differences between the AT commands +CMGR and +CMGL that are discussed in the previous section.

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