Send SMS and MMS Messages From the ESP8266 in C++

The ESP8266 is a microcontroller that can be used to send SMS and MMS messages using C++ and the Arduino IDE. To start, sign up for a Twilio account and find or purchase an SMS-capable number with either SMS or both SMS and MMS capabilities. The ESP-8266 board has TLS 1.2 support, making it suitable for sending secure messages. A WiFi connection is required to connect to Twilio's REST API, and the SHA1 fingerprint of api.twilio.com must be verified before sending a message. The code uses WiFiClientSecure to create a TLS connection and manually constructs an HTTP POST request to send the message. The code also includes functions for base64 encoding and decoding, as well as creating a Basic Auth field for authentication. Once built, the example can be uploaded to the Arduino IDE and will send a SMS or MMS message to a specified number.