Flask is a lightweight Web application framework written with Python, which is called a "micro-framework" because it uses a simple core for extension of other features, such as ORM, form validation tools, file upload, various open authentication techniques, etc.
MQTT is a lightweight Internet of Things (IoT) message transmission protocol based on publish/subscribe mode. It can provide a real-time and reliable message service for networked devices with very less code and smaller bandwidth. It is widely used in IoT, mobile Internet, intelligent hardware, IoV, power and energy industries, etc.