+CMS ERROR: 304, sending message using at command

Question

Im new to GSM and AT command sets,

based on the error +CMS ERROR: 304 its a Invalid PDU mode parameter according to activexperts

Im trying to send message using AT command to GSM modem in PDU mode

AT+CMGF=0
OK

AT+CMGS=31
> 079136190700203911000C913639350768260000AA13C834A89D07B9C3ED32283D0751C3F3F41B

+CMS ERROR: 304        

Can you help me guys what did I missed or mistake? I used this to encode the PDU

Thanks guys.

Answer 1

Try by chaning PDU mode. Use the following command:

AT + CMGF = 1 

If you are trying to Send SMS try AT + CMGF = 1 first and then again AT+CMGS="NUMBER" and hope after typing the message on > prompt, you are using CTRL+Z key combination to send SMS.

Answer 2

Instead of hitting ENTER after placing the PDU, use CTRL-Z to send message.

credits to @user2543882