RaspberryPi Client


The SentiloClientNodeJS is a library written in javascript that brings to you the possibility to connect any device and embedded device with Node.js to a Sentilo instance easily.

For this example we’ll use a Raspberry pi device, because its special features, like cheap price, small dimensions and the great input-output possibilities.


We need some hardware to execute this example:

Material Description
Raspberry Pi Of course, we need a Raspberry Pi, doesn’t matters its version. You need a Raspbian distro installed too
Ethernet cable or wifi dongle Doesn’t matter what network hardware do you use, it’s up to you, but you’ll need the correct drivers correctly configured for connecting to Internet
Some cables Some “dupont” male-to-female cables to make breadboard connections
A LED We’ll use a LED as an output for simulating order execution, you can pick any color
A resistor A 470 Ohms 1/4W resistance
A breadboard You’ll need an electronic connections base to make some circuits, so we’ll recommend you to get a breadboard


We need to install some node.js alternative modules or libraries. We’ll install them through npm or download them from the Internet. See the next section for more information.

Setup the Raspi

In this example we’ll show to you how to implement a sensor and a actuator with several capabilities such as:

  • get values from one o more sensors connected to it GPIO port and publish them in Sentilo
  • receive orders from a Sentilo application and actuate on the GPIO in consequence

If you don’t have node.js installed, install it with:

sudo apt-get install nodejs
sudo apt-get install npm

The software

Create the workspace

First of all, create a directory named sentilo (for example) in our user home and change to it:

pi@raspberrypi ~ $ mkdir sentilo && cd sentilo

Here we’ll work with all our files.

Install the sample code and its dependencies

Download the sample project for this tutorial from the Sentilo git repository, and clone it into your working directory:

pi@raspberrypi ~/sentilo $ git clone https://github.com/sentilo/sentilo-client-sample-nodejs

We need some Node.js modules to work with our library. So you need to download and install the through npm.

You can download via npm update:

pi@raspberrypi ~/sentilo/sentilo-client-sample-nodejs $ npm install

Or install them directly:

pi@raspberrypi ~/sentilo/sentilo-client-nodejs $ npm install express
pi@raspberrypi ~/sentilo/sentilo-client-nodejs $ npm install sync-request
pi@raspberrypi ~/sentilo/sentilo-client-nodejs $ npm install onoff

Which dependencies have been installed?

  • sentilo-client-nodejs: it is a client library for Sentilo (see its main GiHub page or the NPM library page for more information)
  • express: it is a rest server interface for Node.js that allow to us to create a rest server easily (see this link for more information)
  • sync-request: allow to us to create synchronous http calls (see this link for more information)
  • onoff: it is a GPIO driver that allow to us to turn on and off a LED very easily! (see this link for more information)

Now, we can start to develop with node in our working directory

Connecting the hardware

We’ll assume that you have your Raspberry Pi connected to the Internet, a Raspbian system correctly installed and enough permissions to create and runs scripts in your user home. Usually, we will use the pi user.

To simulate a sensor’s actuator, we’ll use a LED connected to the GPIO 14 from the Raspberry Pi.

Let see it below:


As you can see, we only connect the LED annode to the 14 GPIO pin, and the kathode to the GND pin. We’re ready to turn ON and OFF this LED from the Sentilo platform.

The example

Our example is a complete test of the Sentilo Client Node.js library.

The library allows you to perform these operations:

  • Catalog
    • Get sensors from a provider
    • Register sensors for a provider
    • Update sensors configuration
    • Register alerts
  • Alarm
    • Publish alarms
  • Data
    • Retrieve last observations from a sensor
    • Publish observations
  • Subscription
    • Subscribe orders from a sensor
    • Subscribe orders for all the sensors of a provider

The code


This file contains code to control the output LED, that performs a simulation of a possible actuator controlled by the Raspberry Pi and orders published on the Sentilo platform. In the example, the system is being subscribed as endpoint to receive incoming order actuation calls.

var Gpio = require('onoff').Gpio;
var led;

module.exports = {

    init : function() {
         // Configure the GPIO as OUTPUT
         led = new Gpio(14, 'out');

         console.log('Turning OFF the LED');

         // Turn off the LED on startup

      * Execute an order in the actuator. For this example, we've mounted a LED
      * in GPIO 14, where we can turn it ON (order=ON) or OFF (order=OFF)
      * @param order
      *            A Sentilo order object structure
     executeOrder : function(order) {
         console.log('Executing order: ' + order.message);

         if (order.message === 'ON') {
             console.log('Turning ON the LED');
         } else if (order.message === 'OFF') {
             console.log('Turning OFF the LED');



What’s happening here?

  • The init function configures the GPIO 14 as an output to control the LED (don’t forget to call it!)
  • The executeOrder function performs the actuator order execution, for our case, it turns the LED ON and OFF if the order was either ON or OFF. The main server code will access this function.


This file contains the code that performs a possible sensor data read and return its value. For our example, we only emulate a random value as a possible sensor data value. You may develop an data input sensor with a GPIO library.

module.exports = {

     readSensorValue : function() {

         var sensorValue = Math.floor((Math.random() * 255));
         return sensorValue;


What’s happening here?

  • The readSensorValue function reads a possible sensor input data value from an external way. The main server code will access to this function to read the sensor data.

NOTE: as you see, you must implement this function to complete your requirements


This is the main node file. This file performs a rest server and still waiting for incoming calls that apply to the actuator.

// The OS information module
var os = require('os');

// Include some Sentilo operations from the Nodejs client library
var sentilo = require('sentilo-client-nodejs');

// Module that interacts with the local sensor
var sensor = require('./sensor.js');

// Module that interacts with the local actuator
var actuator = require('./actuator.js');

// Get some OS values, like the sensor IP
var interfaces = os.networkInterfaces();
var addresses = [];
for (var k in interfaces) {
    for (var k2 in interfaces[k]) {
        var address = interfaces[k][k2];
        if (address.family === 'IPv4' && !address.internal) {
var myIp = addresses[0];
var myPort = 3000;
var myEndpoint = 'http://'+myIp+':'+myPort;
var myOrderEndointPath = '/order';
var myOrderEndoint = myEndpoint + myOrderEndointPath;
var systemObservationsTimeout = 60000;

// Service and example options
// You must modify it under your requeriments
var samplesOptions = {
    headers : {
    provider : 'samples-provider',
    sensor : 'sample-sensor-nodejs',
    component : 'sample-component',
    componentType : 'generic',
    sensorDataType : 'TEXT',
    sensorType : 'status',
    sensorUnit : '',
    sensorLocation : '41.4122494 2.2101553'

// A very simple RESTFul server module
var express = require('express');
var server = express();
server.use(express.json()) // for parsing application/json
server.use(express.urlencoded({ extended: true })) // for parsing application/x-www-form-urlencoded

server.get('/', (req, res) => {
     var output = `<p>Test server is listening at port: ${myPort}</p>`;
     output += `<p>The server is now ready to receive POST incoming callsat: ${myOrderEndoint}</p>`;

// We only need a POST endpoint service to receive ordercs callbacks
// The path will be [POST] http://localhost:3000/order
server.post('/order', function(req, res, next) {
     var order = req.body;
     console.info("[server][POST] Order received: " + JSON.stringify(order));


    // Execute the order in the actuator

    var value = 'Order received and executed: ' + JSON.stringify(order.message);
    sentilo.publishObservations(value, samplesOptions);

    return next();

function sentiloInit() {
     console.log('[server][sentilo-init] Initializing the NodeJS client example for Sentilo');

     // Init Sentilo services for this example
     // Here you must pass as paramether the specific configuration

     // Test if is there the sensor configured in the catalog
     console.log(`[server][sentilo-init] Registering the ${samplesOptions.sensor} sensor...`);
     var existsSensor = sentilo.existsSensorInCatalog(samplesOptions);
     if (!existsSensor) {
         // If not, then create it
         console.log(`[server][sentilo-init] Sensor ${samplesOptions.sensor} successfully created`);
     } else {
             console.log(`[server][sentilo-init] Sensor ${samplesOptions.sensor} already exists, we'll use it`);

     // Now we can publish a first alarm that informs that the sensor is up
     // First of all let create an external alert
     console.log('[server][sentilo-init] Registering the System Status Alert...');
     var alertsListInputMessage = {
         alerts : [ {
             id : 'SYSTEM_STATUS_ALERT',
             name : 'SYSTEM_STATUS_ALERT',
             description : 'Custom alert to inform the system status',
             type : 'EXTERNAL'
         } ]

     // And then, we can publish an alarm to inform that the system is up now
     var alarmInputMessage = {
         message : 'The system goes up on ' + new Date()
     sentilo.publishAlarm('SYSTEM_STATUS_ALERT', alarmInputMessage);
     console.log('[server][sentilo-init] Alarm published: ' + alarmInputMessage.message);

     // Subscribe the sensor orders
     // We'll manage it throught our server on POST service
     var subscriptionInputMessage = {
         endpoint : myOrderEndoint
     // sentilo.subscribeOrderToAll(subscriptionInputMessage);
     console.log('[server][sentilo-init] Sensor\'s orders succsessfully subscribed to this server');

     // Now, we can publish observations every 60 seconds
     // And still waiting for incoming orders

function publishTestData() {
     console.log('[server][publishTestdata] The sensor is now up, and we\'ll be sending some observations every ' + systemObservationsTimeout + ' ms');
     setInterval(function() {
         // Send some System information
         var freeMemValue = "OS freemem: " + os.freemem();
         console.log('[server][publishTestdata] Retrieved system freemem value: [' + freeMemValue + '] and publishing it as an observation...');
         sentilo.publishObservations(freeMemValue, samplesOptions);

         // Retrieve some sensor data and send it as observation...
         var sensorDataValue = "Sensor value: " + sensor.readSensorValue();
         console.log('[server][publishTestdata] Retrieved sensor value: [' + sensorDataValue + '] and publishing it as an observation...');
         sentilo.publishObservations(sensorDataValue, samplesOptions);
     }, systemObservationsTimeout);

server.listen(myPort, () => {
     console.log(`[server] My ip address is: ${myIp}`);
     console.log(`[server] Test server is listening at: ${myEndpoint}`);
     console.log(`[server] The server is now ready to receive POST incoming calls at: ${myOrderEndoint}`);

     // Initialize the example

First of all, we’ll see the configuration options (line 62). They must be changed before run this example.

You must provide the correct values for these variables located into the samplesOptions object:

  • YOUR-SENTILO-INSTANCE-HOST-IP & YOUR-SENTILO-INSTANCE-HOST-PORT: provide the correct ip address or host of your Sentilo’s instance rest server and port
  • YOUR_SENTILO-INSTANCE-DEFAULT-IDENTITY-KEY: you must provide your private security key (tokenId) that identifies your application or provider (normally same as YOUR-SENTILO-INSTANCE-IDENTITY-KEY). If it is an application, it must have ADMIN permissions over your provider.
  • YOUR_SENSOR_LOCATION: this is optional, identifies the component location of the sample sensor. It can be for example '41.387015 2.170047'

Now, what’s happens in this code?

  • First, we start a rest server with the express module, that allows to us to provide an endpoint for incoming order calls (POST method). After that, we create a subscription for our orders.
  • When a POST request is received, the server will invoke the actuator’s executeOrder function, so we can manage the order correctly (turn ON/OFF the LED, for example)
  • Initialize the sentilo’s helper module (as you can see above), implemented by the sentilo.js file
  • We’re passing to it our specific services configuration, like the sensor id, provider’s token, etc…
  • Request for the sensor in the Sentilo Catalog platform, and if it doesnt’t exists, create it
  • Once we have created the sensor, we’re creating an alert, named SYSTEM_STATUS_ALERT, and publishing an initial alarm that says The system goes up on {date}. Then, the sensor is up and we’re informing it to the system
  • After that, retrieve some system and sensor data values and publish them every 60000ms (1 minute) in a infinite loop

Executing the example

Now we can finally execute the example.

Simple type:

pi@raspberrypi ~/sentilo/sentilo-client-nodejs $ node server.js
[actuator] Turning OFF the LED
[server] My ip address is:
[server] Test server is listening at:
[server] The server is now ready to receive POST incoming calls at:
[server][sentilo-init] Initializing the NodeJS client example for Sentilo
[server][sentilo-init] Registering the sample-sensor-nodejs sensor...
[server][sentilo-init] Sensor sample-sensor-nodejs successfully created
[server][sentilo-init] Registering the System Status Alert...
[server][sentilo-init] Alarm published: The system goes up on Mon Nov 21 2022 16:56:32 GMT+0100 (hora estándar de Europa central)
[server][sentilo-init] Sensor's orders succsessfully subscribed to this server
[server][publishTestdata] The sensor is now up, and we'll be sending some observations every 60000 ms

And now, the server is waiting for publish the observations every 60 seconds:

[server][publishTestdata] Retrieved system freemem value: [OS freemem: 2927603712] and publishing it as an observation...
[server][publishTestdata] Retrieved sensor value: [Sensor value: 51] and publishing it as an observation...

Publishing and accepting orders

The server also is writing for incoming POST calls that responses the ORDER requests. You can practice with orders, sending a PUT message to the Sentilo platform, some like this:


With these values:

HEADER > identity_key : 'YOUR_IDENTITY_KEY'
BODY   > {"order" : "ON"}  > this turns ON the LED
BODY   > {"order" : "OFF"} > this turns OFF the LED

After that, you’ll see in the console some log like this when you’re turning the LED ON, sending order = ON:

[POST] Order received: {"message":"ON","timestamp":"07/05/2015T13:58:20","topic":"/order/samples-provider/sample-sensor-nodejs","type":"ORDER","sensor":"sample-sensor-nodejs","provider":"samples-provider","sender":"samples-provider","time":1431007100595}
Executing order: ON
Turning ON the LED

Or turning it OFF, with order = OFF:

[POST] Order received: {"message":"OFF","timestamp":"07/05/2015T14:01:13","topic":"/order/samples-provider/sample-sensor-nodejs","type":"ORDER","sensor":"sample-sensor-nodejs","provider":"samples-provider","sender":"samples-provider","time":1431007273310}
Executing order: OFF
Turning OFF the LED

Debugging the library

If you need to debug your execution, you can edit the file node_modules/sentilo-client-nodejs/src/utils/SentiloLogs.js and edit the logs configuration properties, as you need:

var options = {
    className : 'Sentilo',
    enableLogs : true,
    enableDebug : true,
    enableInfo : true,
    enableWarn : true,
    enableError : true,
    enableFatal : true

For our purpose, we only have DEBUG, INFO and ERROR logs. Try tu use true or false for each one.