Once a device is online, it still needs a language for sending its data somewhere useful. Web-style protocols were built for browsers, not for tiny battery-powered sensors on unreliable links, so the IoT world uses lighter messaging protocols designed for that job.
You'll start with MQTT, the publish/subscribe protocol where devices send messages to topics through a broker, and then publish and subscribe from an ESP32. Next comes CoAP, a lightweight alternative built for very constrained devices. Finally you'll connect a device to the cloud with AWS IoT Core, covering how a device is registered and secured with certificates and policies before it can send data.
Once you've finished, move on to Security, Power & Production to make your device safe, efficient, and ready to ship.
The publish/subscribe model behind most IoT messaging: how clients, topics, and a central broker fit together, and what the quality-of-service levels guarantee.
A hands-on tutorial using MQTT on the ESP32 with ESP-IDF: connecting to a broker, subscribing to a topic, and publishing messages to it.
Registering a device in the cloud step by step: creating a Thing, attaching a policy, and generating the certificates the ESP32 uses to connect securely to AWS IoT Core.