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Internet of Things with Android and Arduino: IoT Arduino project

Learn how to build an Internet of things project with Android and Arduino. Build an Arduino IoT project to control a remote LED

Android with Aruino IoT

This IoT Arduino project describes how to connect Android and Arduino. To make things simple, we will suppose that we want to control a LED connected to Arduino using an Android app. This is a common scenario that requires to integrate Android and Arduino in an IoT Arduino project. Nowadays Internet of Things (IoT) is a pervasive technology that is changing the way we live and how we interact with devices. In IoT project, all the physical objects (things) are connected together using internet infrastructure. Arduino board is one of the most important devices that enables us to prototype projects. This post explores how to integrate Android with Arduino making the first step in IoT.

Internet of Things with Android and Arduino: Arduino IoT Project Overview

The picture below shows the main objects involved in the Arduino IoT project:

Internet of Things with Android and Arduino

What we need is:

  • Arduino Uno
  • Ethernet shield
  • Smartphone with Android
These devices are on the same network for simplicity. The idea of this Arduino and Android IoT project is building an Android app that exchanges data with Arduino. To this purpose, the Android app will communicate with Arduino using the HTTP protocol. A small and simple Web server runs on Arduino, accepting HTTP requests. For simplicity, the app sends JSON data that holds the led status. Below you can download the Arduino source code for this Arduino IoT project.

Download the Arduino source code project .ino

How to build an Arduino IoT project

The first step in building an Arduino IoT project that connects to Android, therefore we are building an Arduino server that accepts HTTP connection. Moreover, considering that this project wants to control a simple LED using an Android app, it is necessary to connect Arduino to a LED. The schematic below shows how to do it
How to connect Arduino to a LED and control it using Android app. Arduino IoT project
As you can see the connection is very simple. The Arduino code below describes how to build a simple HTTP server on Arduino to accept connecting coming from the Android app.
#include <spi.h>
#include <ethernet.h>
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 1, 130); // Arduino IP Add
EthernetServer server(80); // Web server

// Http data
String reqData; // Request from Smartphone
String header;
int contentSize = -1;
String CONTENT_LENGTH_TXT = "Content-Length: ";

void setup() {
  // put your setup code here, to run once:
  pinMode(3, OUTPUT); // Set Pin 3 to OUTPUT Mode
  Ethernet.begin(mac, ip);

void loop() {
  // Is there a client (Our Android smartphone)
  EthernetClient client = server.available(); 

  if (client) {
    // Let's start reading
    boolean isLastLine = true;
    boolean isBody = false;
    header = "";
    reqData = "";
    int contentLen = 0;
    Serial.print("Client connected!");
    while (client.connected()) {
     if (client.available()) {
       // Read data
      char c = client.read();

     if (contentSize == contentLen) {
       int idx = reqData.indexOf(":");
       String status = reqData.substring(idx + 1, idx + 2);
       Serial.println("Status : " + status);
       if (status.equals("1")) {
         digitalWrite(3, HIGH);
       else {
         digitalWrite(3, LOW);

     client.println("HTTP/1.1 200 OK");
     client.println("Content-Type: text/html");
     client.println("Connection: close");
     // send web page

  if (c == 'n' && isLastLine) {
   isBody = true;
   int pos = header.indexOf(CONTENT_LENGTH_TXT);
   String tmp = header.substring(pos, header.length());
   int pos1 = tmp.indexOf("rn");
   String size = tmp.substring(CONTENT_LENGTH_TXT.length(), pos1);
   Serial.println("Size ["+size+"]");
   contentSize = size.toInt();

  if (isBody) {
   reqData += c;
  else {
   header += c;
  if (c == 'n' ) {
   isLastLine = true;
  else if (c != 'r' ) {
    isLastLine = false;

// Close connection

Almost all the arduino source code is used to handle HTTP connections. Notice that at line 4 we set the MAC Address of the ethernet shield while at line 5 we set the IP address. The server runs on port 80, you can change this port if you want. Once we have created this server Arduino can exchange JSON requests with the external application including an app that runs on a smartphone.

In this first part of Internet of things with Android and Arduino project, you gained the knowledge on how to handle HTTP requests in Arduino. If you like to build a more complex project, you can explore how to build a smart plant monitoring system.

Android app client: Send HTTP request

To complete our Internet of things with Android and Arduino scenario, it is necessary to implement an Android app that sends JSON requests.
On the Android code side, the things are much simpler; the Android UI is shown below:

Android app to control Arduino

There is one simple button. When the user clicks on it, the app sends an HTTP request to Arduino, that runs the web server.
If you want to know more about HTTP look at making HTTP requests in Android.
The app layout is very simple and it is not covered here, the core of the app is where the button click is handled:

ledView = (ImageView) findViewById(R.id.ledImg);
// Set default image

// Init HTTP client
client = new HttpClient();

ledView.setOnClickListener(new View.OnClickListener() {
  public void onClick(View v) {
   client.doRrequest(status ? "1" : "0");
   status = !status;
   if (status)


When the user touches the button, the app sends an HTTP request using HTTP client. In this case, this project uses OkHttp. The HTTP client is very simple:

public void doRrequest(String status) {
  Log.d("AA", "Making request..["+status+"]");
  Request req = new Request.Builder()
        create(JSON, createJSON(status)))

   client.newCall(req).enqueue(new Callback() {
     public void onFailure(Request request,
                           IOException e) { }

     public void onResponse(Response response) throws IOException {
        Log.d("AA", "resp [" + response.body().string() + "]");

Below some images of my work showing Arduino in IoT environment :

Android and Arduino integration Arduino with Android to control a LED

This Internet of things project with Android and Arduino showed how to integrate two different ecosystems and make them work together. In this post, you gained a basic understanding of how to create Arduino webserver example and how to connect it to the android app. This project can be extended and could be used as a base for arduino home automation. It is possible to make even more complex project that uses Android app and Arduino to control an RGB led.


  1. Any way to impliment this with Outlook. Say, whenever you have an unopened email in your inbox, the light goes on?

  2. it's very simple and good project for starter.
    so, If you don't mind, I would like to introduce on WIZnet museum (http://wiznetmuseum.com) for everyone.
    WIZnet produce the W5100 chipset on Ethernet shield. Hopefully, you will allow this.

  3. Sir, i am getting error in the arduino code at line no 63 saying, “amp was not declared in its scope”, my question is what is amp, can you please help me remove this error. Thank You

  4. Is there any example about how to send an email by using Ethernet shield , like when motion sensor detects motion the arduino send me email , helping me will be appreciated

  5. Hello sir,
    I am vivek anand from india. I just want to know that which bluetooth module is better with Arduino for multiple command.

    • Hi Vivek,

      as far as i know you can use every bluetooth module you like. You could prefer a bluetooth shield that is connected on top of arduino board or a external module. It is up to you.
      For my project i use an external module.

  6. hello sir,
    i’m usmar ismail from indonesia.
    this is awesome,
    i have project that i have to create program like this, can you give me a tutorial for android session in this project. i dont get it, please,
    i apologize for my english
    email :[email protected]

  7. sir i’m using enc28j60 with uipethernet shield.and control lights via android apk.
    but problem is that when i press button for led onn/off it will react after 2 to 3 second later.
    if i use same apk with wi-fly module rn-171.it reacts within milisecond.
    how can i improve speed in ethernet.

  8. hello sir. i want to create a combination of smart mirror and smart window for my iot project with my partner. we want to use the idea of smart mirror and put the idea on the window. the idea of smart window is still there and we just want upgrade the functionality of smart window become smart mirror as well. both of us are lack of knowledge of the arduino. our final year project coordinator wants us to use arduino and preferred the arduino mega. will u help us out with this? we really need help.

  9. Hello sir i want to do project with IOT in the AWS inftastructure…could you please help me to select the idea which king of thing is doable with in 6 weeks.??

  10. hello , thanks for sharing , i try to compile your arduino code but i got this error
    error: unknown type name ‘prog_char’
    uint16_t fill_tcp_data_p(uint8_t *buf,uint16_t pos, const prog_char *progmem_s)
    Utilisation de la bibliothèque SPI version 1.0 dans le dossier: C:Program Files (x86)ArduinohardwarearduinoavrlibrariesSPI
    Utilisation de la bibliothèque Ethernet version 1.1.2 dans le dossier: C:Program Files (x86)ArduinolibrariesEthernet
    exit status 1
    Error compiling for board Arduino/Genuino Uno

    can you help me fix it ?

    • HI it seems a prole related to your libraries. You can try to create a new empty sketch and check if it compiles. I sup pose it is a problem not related to the sketch in the post. Let me know the results

      • thank you sir ,i fixed the probleme , by downloading the zip file posted in this page, and it has successfuly compiled , the probleme is with posted code cus it s contained some syntaxe error for ex : library is declared : #include <spi.h> #include <ethernet.h>
        and the instruction :
        if (c == ‘n’ && isLastLin )
        could you send me the android complete code , i need it for my final study
        project ?

      • Hello sir , sorry it was my fault , i compiled the arduino code on the page not the code in the zip file , sir can you send me the full source android code i need it as a part of my final study project , thanks

  11. hi sir,
    i am a last year eng student,i have a plan to do a project which uses a android application that control a electronic device through internet.i want to get data from the device and store in a server also eant to retrive the data in the app.
    can you please help me with the android code and the other server side procedure that i need to follow to complete the project

  12. Hello Sir!

    I’m trying to develop an android application for my IoT project. The project is to sense temperature using LM35 temp sensor, send data to thinkspeak using Arduino UNO and ESP8266 wifi shield. The data is analysed at thinkspeak and I want to display it in the app too. Then the app’s user will determine whether a fan has to turned on or not depending on the temperature readings. So far I’m able to send data to thinkspeak and analyse it only the app development part is left. I’m completely new to Andriod app development.

    Could you please help me in accomplishing the task?!

  13. Hello Sir, i am rizal from indonesian, can you tell more about source code android app in this project.? i am confused because the code is not full. or the project is it on github repo?
    i am looking complete android app source code.

  14. Hi,

    Nice to meet you.

    We are the WIZnet Team in India.

    We have been searching some application references in which WIZnet solution is applied and found your project “Control RGB LED using Arduino and Android “. I. Your development looks very cool & smart.

    Recently we have developed WIZnet Museum (http://wiznetmuseum.com) site. This is an academic-purposed collection of open projects, tutorials, articles and etc from our global customers.
    If you are O.K. we would like to introduce your project and device in here. Hopefully, you will allow this.
    Hopefully, keep contacting us for the friendship.

    Thank you very much
    Wiznet team, India


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