In this article, by Soham Chetan Kamani, author of the book Full Stack Web Development with Raspberry Pi 3, we will cover the marvel of the Raspberry Pi, however, doesn’t end here. It’s extreme portability means we can now do things which were not previously possible with traditional desktop computers. The GPIO pins give us easy access to interface with external devices. This allows the Pi to act as a bridge between embedded electronics and sensors, and the power that linux gives us. In essence, we can run any code in our favorite programming language (which can run on linux), and interface it directly to outside hardware quickly and easily. Once we couple this with the wireless networking capabilities introduced in the Raspberry Pi 3, we gain the ability to make applications that would not have been feasible to make before this device existed.and Scar de Courcier, authors of Windows Forensics Cookbook
The Raspberry Pi has become hugely popular as a portable computer, and for good reason. When it comes to what you can do with this tiny piece of technology, the sky’s the limit. Back in the day, computers used to be the size of entire neighborhood blocks, and only large corporations doing expensive research could afford them. After that we went on to embrace personal computers, which were still a bit expensive, but, for the most part, could be bought by the common man. This brings us to where we are today, where we can buy a fully functioning Linux computer, which is as big as a credit card, for under 30$. It is truly a huge leap in making computers available to anyone and everyone.

(For more resources related to this topic, see here.)

 Web development and portable computing have come a long way. A few years ago we couldn’t dream of making a rich, interactive, and performant application which runs on the browser. Today, not only can we do that, but also do it all in the palm of our hands (quite literally). When we think of developing an application that uses databases, application servers, sockets, and cloud APIs, the picture that normally comes to mind is that of many server racks sitting in a huge room. In this book however, we are going to implement all of that using only the Raspberry Pi.
In this article, we will go through the concept of the internet of things, and discuss how web development on the Raspberry Pi can help us get there. Following this, we will also learn how to set up our Raspberry Pi and access it from our computer.
We will cover the following topics:

• The internet of things
• Our application
• Setting up Raspberry Pi
• Remote access

The Internet of things (IOT)

The web has until today been a network of computers exchanging data. The limitation of this was that it was a closed loop. People could send and receive data from other people via their computers, but rarely much else.

The internet of things, in contrast, is a network of devices or sensors that connect the outside world to the internet. Superficially, nothing is different: the internet is still a network of computers. What has changed, is that now, these computers are collecting and uploading data from things instead of people. This now allows anyone who is connected to obtain information that is not collected by a human.

The internet of things as a concept has been around for a long time, but it is only now that almost anyone can connect a sensor or device to the cloud, and the IOT revolution was hugely enabled by the advent of portable computing, which was led by the Raspberry Pi.

 A brief look at our application

Throughout this book, we are going to go through different components and aspects of web development and embedded systems. These are all going to be held together by our central goal of making an entire web application capable of sensing and displaying the surrounding temperature and humidity.

In order to make a properly functioning system, we have to first build out the individual parts. More difficult still, is making sure all the parts work well together. Keeping this in mind, let's take a look at the different components of our technology stack, and the problems that each of them solve :

The sensor interface - Perception

The sensor is what connects our otherwise isolated application to the outside world. The sensor will be connected to the GPIO pins of the Raspberry pi. We can interface with the sensor through various different native libraries.

This is the starting point of our data. It is where all the data that is used by our application is created. If you think about it, every other component of our technology stack only exists to manage, manipulate, and display the data collected from the sensor.

The database - Persistence

"Data" is the term we give to raw information, which is information that we cannot easily aggregate or understand. Without a way to store and meaningfully process and retrieve this data, it will always remain "data" and never "information", which is what we actually want.

If we just hook up a sensor and display whatever data it reads, we are missing out on a lot of additional information. Let's take the example of temperature: What if we wanted to find out how the temperature was changing over time? What if we wanted to find the maximum and minimum temperatures for a particular day, or a particular week, or even within a custom duration of time? What if we wanted to see temperature variation across locations? There is no way we could do any of this with only the sensor. We also need some sort of persistence and structure to our data, and this is exactly what the database provides for us.

If we structure our data correctly, getting the answers to the above questions is just a matter of a simple database query.

The user interface - Presentation

The user interface is the layer which connects our application to the end user. One of the most challenging aspects of software development is to make information meaningful and understandable to regular users of our application.

The UI layer serves exactly this purpose: it takes relevant information and shows it in such a way that it is easily understandable to humans. How do we achieve such a level of understandability with such a large amount of data? We use visual aids: like colors, charts and diagrams (just like how the diagrams in this book make its information easier to understand).

An important thing for any developer to understand is that your end user actually doesn't care about any of the the back-end stuff. The only thing that matters to them is a good experience. Of course, all the 0ther components serve to make the users experience better, but it's really the user facing interface that leaves the first impression, and that's why it's so important to do it well.

The application server - Middleware

This layer consists of the actual server side code we are going to write to get the application running. It is also called "middleware". In addition to being in the exact center of the architecture diagram, this layer also acts as the controller and middle-man for the other layers.

The HTML pages that form the UI are served through this layer. All the database queries that we were talking about earlier are made here. The code that runs in this layer is responsible for retrieving the sensor readings from our external pins and storing the data in our database.

Summary

We are just warming up! In this article we got a brief introduction to the concept of the internet of things. We then went on to look at an overview of what we were going to build throughout the rest of this book, and saw how the Raspberry Pi can help us get there.

Resources for Article:

Further resources on this subject:

• Clusters, Parallel Computing, and Raspberry Pi – A Brief Background [article]
• Setting up your Raspberry Pi [article]
• Welcome to JavaScript in the full stack [article]