Eclipse Authors: Pat Romanski, Elizabeth White, Liz McMillan, David H Deans, JP Morgenthal

Blog Feed Post

Remote Controlling a Car over the Web. Ingredients: Smartphone, WebSocket, and Raspberry Pi.

At Kaazing, we have been experimenting with using a smartphone as a remote control for quite some time now. Those familiar with our demos may have seen our Zing-Pong demo (which is a “Pong”-style game using smartphones to control the paddles over WebSocket) or our Racer demo (which is a 3D Formula One car rendered in WebGL as a Chrome Experiment, and remotely controlled with a smartphone). These demos, along with the other demos we’ve created with Kaazing’s platform, use no plug-ins. You simply point a browser on your computer to the address of the object you want to control (for example, the gorgeous Formula One car rendered in WebGL) and a browser from your smartphone to the address of the remote control (an ID we generate for you). Once connected, you just…go!

A couple of our Visionary Zingers, Prashant Khanal and David Witherspoon, then experimented with communicating with a Raspberry Pi using WebSocket–or, more specifically, using Kaazing’s JMS-over-WebSocket Gateway to tell Raspberry Pi to turn on and off a lightbulb. When the lightbulb turned on in this experiment, another lightbulb turned on: could we in fact turn a remote, radio-controlled car into a remote, WebSocket-controlled car? By controlling the car over the Web, could we control the car from another room? From another continent?

The Racer Demo

Let’s first take a closer look at the Racer demo. The Racer demo uses the reflector pattern: where we connect devices through a WebSocket server, thus simulating peer-to-peer connectivity, a very easy-to-achieve task using pub/sub. When we developed the Racer demo, we walked through the steps to build it in The Simplest Way to Use Your Smartphone as a Game Controller: A WebSocket Race Car Demo. By examining how to use pub/sub concepts to control a virtual car, it’s not so farfetched to consider doing the same with a radio-controlled car.

The Goal

After working with the Racer demo, we knew what we wanted to achieve: controlling a “real” car (or at least a good-sized monster truck model) with a simple web app on a smartphone. Something like this, for example:


And something that might move like this:

In just a few hours of hacking and experimenting, we turned this radio-controlled car into a WebSocket-controlled car. Don’t worry, no actual cars (or bunnies) were harmed in the making of this demo, as you’ll see as we walk through the hardware and software we used.

Ingredients: The Hardware

  • One RC car. We ended up using a black F150. The bigger the car, the easier it is to connect, position, and hide the building blocks. One thing to pay attention to is that the car you’re about to buy has to have two simple motors, one that drives the vehicle forward/backward, and another one that steers the car: front wheels left/right. The first thing you’ll get rid of is the radio control, so don’t worry about that too much.
  • One Raspberry Pi, model B. This piece of hardware is incredible. Runs Linux (and Java), has 512MB RAM, an Ethernet port, 2 USB ports (for keyboard, mouse, WiFi), takes an SD card, has an HDMI out, and has a handful of GPIO (General Purpose Input/Output) pins to drive external devices, like lights, motors, and alike.
  • One small breadboard. This simplifies connecting the building blocks.
  • Set of male to male and male to female jumper leads.
  • L298N Board: It is used to control the car motors. The car is equipped with two motors – one for steering and the other to drive wheels. Each motor is controlled  through two GPIO pins.
  • A couple of LEDs – optional. This RC car model didn’t come with any lights, but who has seen a serious RC car without lights – so we equipped ours with remote controllable LEDs.
  • One smartphone (can be substituted by a tablet, or any Web browser, really). Using a touch-based device makes the controlling more natural, but you can use any laptop/desktop browser with mouse/trackpad as well.
  • Battery. Anker Astro 5600 mAh external battery pack powering the Raspberry Pi and connected circuits: LEDs and relays.

The circuit diagram regarding the wiring among the Raspberry Pi GPIO pins, L298N board and the car battery can be found here. The pin numbers specified for the Raspberry Pi in the circuit diagram refers to the physical pin location.

Ingredients: The Software

  • WebSocket Server. We used Kaazing’s high performance enterprise grade WebSocket Gateway – JMS Edition. The JMS Edition provides an easy-to-use pub/sub abstraction, along with support for multiple WebSocket client technologies (of which we used the JavaScript and Java clients in the project). The WebSocket Gateway ships with Apache ActiveMQ, an open source message broker.
  • WebSocket JavaScript client code. The Kaazing JavaScript client code runs in the browser on the smartphone (or any other web browser), playing the role of the remote control. The user’s actions trigger events on the remote control and result in messages being sent to the WebSocket server.
  • WebSocket Java client code. The Kaazing Java client runs on the Raspberry Pi, receiving messages from the WebSocket server, and instructing the Raspberry Pi GPIO pins to control the car.  Control of the GPIO pins is achieved through the Pi4J Library.

Reviewing the Hardware

We decided to hide all the electronics in the body of the car, but wanted to have the Raspberry Pi accessible and more importantly, visible. It’s sitting on the truck’s plateau, lightly taped to it, so it doesn’t fall off as the truck accelerates and comes to sudden stops (read: bumps into things).


On the right you can see the WiFi plugged into the top USB port (blue LED). On the left, you see the blue SD card. The GPIO ports are on the top left, connected to drive the two motors and the lights of the truck. The Raspberry Pi is powered through a micro USB port on the bottom left, leveraging a smartphone quick charger battery.

IMG_6020Under the “hood”, you can see the relay, and the breadboard connecting to the Pi, and the motors of the truck, as well as the front LEDs.

Reviewing the Software

To enable the Raspberry Pi to receive WebSocket messages from the browser client, we had to write some logic that runs on the Pi.


The two clients, the smartphone remote control, and the code running on the Raspberry Pi, communicate with each other via WebSocket. In addition to JavaScript clients, Kaazing supports Java, .NET, and Flash/Flex clients. We chose the Java client for the Pi. The communication between these clients is seamless. The back-end message broker, which provides the messaging services is Apache ActiveMQ, but could be another JMS message broker like TIBCO’s, Informatica’s, or IBM’s, as well.


JavaScript Remote Control Code on the Smartphone

Since we plan to use this demo at trade shows, we wanted to make sure that we have a certain level of control over who controls the car and when. Therefore, we use a “secret” key that the remote control has to know to control the car. This key is sent to the code running on the Pi via a secured admin topic. Every message coming from the smartphone has to contain the same key. If it doesn’t, the message is thrown away.

The remote control client on the smartphone first asks for the key that identifies who can control the car.


Then, the HTML5 remote control code, which runs on the smartphone, first establishes a connection to the WebSocket server. It creates a JMS topic, and a producer (or publisher) for the topic. When done, the client is ready to start sending messages through the WebSocket gateway to the Java code running on the Pi. Every message contains the previously specified key as well, as a custom JMS message property.

The images rendered for the remote control UI in the browser have JavaScript event listeners defined. The listeners are invoked both when the images are touched (touchstart), as well as when the images as released (touchend). The JavaScript client code sends messages as frequently as it can while one or more buttons are pressed, and one message as a control icon is let go.


If you want to learn more and understand the JavaScript JMS APIs, try out the Step-by-Step Tutorial of Building a Simple Peer-to-Peer WebSocket Application tutorial or our API documentation.

Java Code Running on the Raspberry Pi

We chose to program the Raspberry Pi using Java.  Instructions to install Java on the Raspberry Pi can be found here.  The Java code on the raspberry requires both the JMS Kaazing Websocket Library to receive messages from the client, and the Pi4J library to interact with the car through the Rasbperry Pi’s GPIO .

The code is split into two main classes, CommandReceiver and Car.  CommandReceiver is responsible for connecting to the Kaazing JMS Gateway and listening to both on the command and the admin topic.  When admin messages are received the CommandReceiver will record which user has valid access to control the car.  When a command message is received, its properties will be checked to see if it is the current user in control of the car. If so, the message will be parsed and read, resulting in a corresponding method being called on the Car class.

The Car class is an abstraction of everything the car may do.  It has methods such as Steering, Thrust, and Lights that are called with Command parameters such as ON, OFF, LEFT, and RIGHT. When called, the GPIO inputs corresponding to each method and are switched on or off, thereby resulting on the motors of the car moving forward, backwards, or steering left or right.

To check out or download the full source code visit KaazingPi on Github.

The Result

Well, we cheated and already showed the video of the result at the beginning. But, if you want to see it in person, come see us at one of our upcoming events:

Read the original blog entry...

More Stories By Kaazing Blog

Kaazing is helping define the future of the event-driven enterprise by accelerating the Web for the Internet of Things.

@ThingsExpo Stories
The standardization of container runtimes and images has sparked the creation of an almost overwhelming number of new open source projects that build on and otherwise work with these specifications. Of course, there's Kubernetes, which orchestrates and manages collections of containers. It was one of the first and best-known examples of projects that make containers truly useful for production use. However, more recently, the container ecosystem has truly exploded. A service mesh like Istio addr...
Predicting the future has never been more challenging - not because of the lack of data but because of the flood of ungoverned and risk laden information. Microsoft states that 2.5 exabytes of data are created every day. Expectations and reliance on data are being pushed to the limits, as demands around hybrid options continue to grow.
Poor data quality and analytics drive down business value. In fact, Gartner estimated that the average financial impact of poor data quality on organizations is $9.7 million per year. But bad data is much more than a cost center. By eroding trust in information, analytics and the business decisions based on these, it is a serious impediment to digital transformation.
Business professionals no longer wonder if they'll migrate to the cloud; it's now a matter of when. The cloud environment has proved to be a major force in transitioning to an agile business model that enables quick decisions and fast implementation that solidify customer relationships. And when the cloud is combined with the power of cognitive computing, it drives innovation and transformation that achieves astounding competitive advantage.
Digital Transformation: Preparing Cloud & IoT Security for the Age of Artificial Intelligence. As automation and artificial intelligence (AI) power solution development and delivery, many businesses need to build backend cloud capabilities. Well-poised organizations, marketing smart devices with AI and BlockChain capabilities prepare to refine compliance and regulatory capabilities in 2018. Volumes of health, financial, technical and privacy data, along with tightening compliance requirements by...
As IoT continues to increase momentum, so does the associated risk. Secure Device Lifecycle Management (DLM) is ranked as one of the most important technology areas of IoT. Driving this trend is the realization that secure support for IoT devices provides companies the ability to deliver high-quality, reliable, secure offerings faster, create new revenue streams, and reduce support costs, all while building a competitive advantage in their markets. In this session, we will use customer use cases...
Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settlement products to hedge funds and investment banks. After, he co-founded a revenue cycle management company where he learned about Bitcoin and eventually Ethereal. Andrew's role at ConsenSys Enterprise is a mul...
DXWorldEXPO LLC announced today that "Miami Blockchain Event by FinTechEXPO" has announced that its Call for Papers is now open. The two-day event will present 20 top Blockchain experts. All speaking inquiries which covers the following information can be submitted by email to [email protected] Financial enterprises in New York City, London, Singapore, and other world financial capitals are embracing a new generation of smart, automated FinTech that eliminates many cumbersome, slow, and expe...
DXWorldEXPO | CloudEXPO are the world's most influential, independent events where Cloud Computing was coined and where technology buyers and vendors meet to experience and discuss the big picture of Digital Transformation and all of the strategies, tactics, and tools they need to realize their goals. Sponsors of DXWorldEXPO | CloudEXPO benefit from unmatched branding, profile building and lead generation opportunities.
The best way to leverage your Cloud Expo presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering Cloud Expo and @ThingsExpo will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at Cloud Expo. Product announcements during our show provide your company with the most reach through our targeted audiences.
DevOpsSummit New York 2018, colocated with CloudEXPO | DXWorldEXPO New York 2018 will be held November 11-13, 2018, in New York City. Digital Transformation (DX) is a major focus with the introduction of DXWorldEXPO within the program. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of bus...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors! In this blog post, we provide 7 tips on how, as part of our world-class faculty, you can deliver one of the most popular sessions at our events. But before reading...
Cloud Expo | DXWorld Expo have announced the conference tracks for Cloud Expo 2018. Cloud Expo will be held June 5-7, 2018, at the Javits Center in New York City, and November 6-8, 2018, at the Santa Clara Convention Center, Santa Clara, CA. Digital Transformation (DX) is a major focus with the introduction of DX Expo within the program. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive ov...
DXWordEXPO New York 2018, colocated with CloudEXPO New York 2018 will be held November 11-13, 2018, in New York City and will bring together Cloud Computing, FinTech and Blockchain, Digital Transformation, Big Data, Internet of Things, DevOps, AI, Machine Learning and WebRTC to one location.
DXWorldEXPO LLC announced today that ICOHOLDER named "Media Sponsor" of Miami Blockchain Event by FinTechEXPO. ICOHOLDER give you detailed information and help the community to invest in the trusty projects. Miami Blockchain Event by FinTechEXPO has opened its Call for Papers. The two-day event will present 20 top Blockchain experts. All speaking inquiries which covers the following information can be submitted by email to [email protected] Miami Blockchain Event by FinTechEXPO also offers s...
Dion Hinchcliffe is an internationally recognized digital expert, bestselling book author, frequent keynote speaker, analyst, futurist, and transformation expert based in Washington, DC. He is currently Chief Strategy Officer at the industry-leading digital strategy and online community solutions firm, 7Summits.
Digital Transformation and Disruption, Amazon Style - What You Can Learn. Chris Kocher is a co-founder of Grey Heron, a management and strategic marketing consulting firm. He has 25+ years in both strategic and hands-on operating experience helping executives and investors build revenues and shareholder value. He has consulted with over 130 companies on innovating with new business models, product strategies and monetization. Chris has held management positions at HP and Symantec in addition to ...
Cloud-enabled transformation has evolved from cost saving measure to business innovation strategy -- one that combines the cloud with cognitive capabilities to drive market disruption. Learn how you can achieve the insight and agility you need to gain a competitive advantage. Industry-acclaimed CTO and cloud expert, Shankar Kalyana presents. Only the most exceptional IBMers are appointed with the rare distinction of IBM Fellow, the highest technical honor in the company. Shankar has also receive...
Enterprises have taken advantage of IoT to achieve important revenue and cost advantages. What is less apparent is how incumbent enterprises operating at scale have, following success with IoT, built analytic, operations management and software development capabilities - ranging from autonomous vehicles to manageable robotics installations. They have embraced these capabilities as if they were Silicon Valley startups.
With tough new regulations coming to Europe on data privacy in May 2018, Calligo will explain why in reality the effect is global and transforms how you consider critical data. EU GDPR fundamentally rewrites the rules for cloud, Big Data and IoT. In his session at 21st Cloud Expo, Adam Ryan, Vice President and General Manager EMEA at Calligo, examined the regulations and provided insight on how it affects technology, challenges the established rules and will usher in new levels of diligence arou...