SMS using GSM Modems - Problem with AT+CMGS command, CMS ERROR
This guide gives you hints on how you can resolve problems with SMS sending.
We assume that you are using a GSM modem for SMS messaging, the modem is
attached to the serial port of the computer with a phone-to-pc data cable
and SMS receiving works.
Ozeki NG SMS Gateway uses the AT+CMGS command to send SMS messages. This command
sends a PDU encoded SMS message to the mobile network. If the mobile network
accepts the message a callback reference id is returned. (This id is used in
If everything goes well the communication looks returns an OK response with
a callback reference id (Figure 1). Please note that
the number 134 was returned by the GSM network as the callback reference
ID after sending the SMS PDU.
If something goes wrong you will see an error message instead of the positive
acknowledgment (Figure 2).
2007.12.06. 17:40:09 - <- AT+CMGS=24
2007.12.06. 17:40:09 - <-
2007.12.06. 17:40:09 - <- >
2007.12.06. 17:40:09 - -> 0021000B916302450696F100000C25180C168BC16437AA3408
2007.12.06. 17:40:13 - <- 0021000B916302450696F100000C25180C168BC16437AA3408
2007.12.06. 17:40:13 - <- ERROR
2007.12.06. 17:40:13 - <-
2007.12.06. 17:40:13 - ERROR 1845: Message could not be sent. Reason:
ERROR 1818: Envelope could not be sent. 0021000B916302450696F100000C25180C168BC16437AA3408\r\nERROR\r\n
Figure 2 - Could not send message
How to resolve this SMS Sending problem
In order to resolve this issue, you must find out what can cause this problem.
The following list contains the most common reasons with tips on how to solve them.
Common reason #1: Invalid SMSC setting
The Short Message Service Center (SMSC) address is often not configured
properly in the software. Please note that the correct SMSC should be specified
for your GSM network and the SMSC number must be entered in International
format with a leading plus sign.
Common reason #2: Insufficient money on SIM Card
To test if this is the problem, put your SIM card into a regular GSM handset and
send an SMS message. If you could send a message this is not the problem you are
Common reason #3: The SIM card has a PIN code
Please put the SIM into a regular GSM handset and make sure it does not require
a PIN code when the phone is restarted. You should NOT have any PIC code
protection configured on the SIM.
Common reason #4: No network coverage
You should check your antenna and the you can verify the signal strength and
network registration by issuing the AT+CREG and the AT+CSQ commands in
Common reason #5: The GSM modem is frozen
Please power off your GSM modem and power it back on. (Ozeki NG SMS Gateway
performs a port open/port close procedure when it detects this error, because
this procedure often resets the GSM modem.)
Common reason #7: Your modem might not support PDU mode
Please check the logs and see what was the response to AT+CMGF=0. If the
response was NOT an OK, then your modem cannot be used for sending SMS
messages in PDU mode.
It might be possible that you did not receive a plain 'ERROR' response, but you
have received a 'CMS+ERROR' response. In this case please read the following
webpage to figure out what causes the error:
CMS Error codes