The SIM800L is a GSM module that can be used to send and receive text messages, make phone calls, and connect to the internet. In this project, we will use the
SIM800L to send text messages from an ESP8266 [nerdytechy.com]. The ESP8266 will act as a server, and the SIM800L will act as a client. First, we need to install the SIM800L library for Arduino. Then, we need to create a new Arduino sketch and import the library. Next, we need to define some global variables for the SIM800L library. We will also need to create an instance of the Client class.
In the setup() function, we will initialize the serial port and set up our Wi-Fi connection. We will also initialize the Client object and set its port number to 9600.