Summary

Now you can transmit encrypted MQTT messages to an MQTT broker, and from there to another ESP8266 or to a database or a server. Doing this, no one can intercept and alter your data, so your home or your data are secure. Security in IoT is very important nowadays, since there are a lot of devices that are not secured even with a user and a password. If you need to work offline, now you have an entire microSD card to write or read data from it. Using a battery-powered ESP8266 and deep sleep features, now you can log data to a microSD card up to few a months. Encrypt them to be sure that you are the only one that has access to them. 

In the next chapter will see how to stream data over a WebSocket connection, data that can be stored in a time series database or displayed as a real-time graphic.