AT Command sequence for proper network connection / disconnection

What are AT Commands?

According to Codeproject.com, AT Commands are "instructions used to control a modem. AT is the abbreviation of ATtention. Every command line starts with "AT" or "at". That's why modem commands are called AT commands."

AT command sequence for proper network connection: 

Please check the manual from your module vendor for the exact AT command to use.

When configuring a new device, you need to configure the AT command sequence to fit with your use-case. 

To avoid any wrong configuration in the device, we recommend you to implement the following AT command sequence to connect and disconnect properly from/to the mobile network:

1. AT+CSQ     [ To measure the signal quality ]
2. AT+CREG=1    [ To enable network registration ]
3. AT+CREG?    [ To return the current state of the network registration : Attach/Detach ]
4. AT+COPS=? [ To return the list of available operators ]
5. AT+COPS= [ To manually select an available operator ]
6. AT+COPS? [ To check the current network ]
7. AT+CGATT=1    [ to attach the terminal to GPRS service ] 
8. AT+CGATT?    [ To return the current state of GPRS service : Attach/Detach ]
9. AT+CGDCONT=1,"IP","em"    [ To define PDP Context ]
10. AT+CSQ    [ to measure signal quality ]  
11. AT+CGACT=1    [ To activate a PDP context ]  
12. AT+CGDCONT?    [ To return the current state of the PDP context]
13. AT+CGACT=0    [ To deactivate a PDP context ]