Skip to main content

Constrained Application Protocol (CoAP) using Node JS

Constrained Application Protocol using Node JS

Constrained application protocol is shortly called as CoAP and its based on Request Response Model where a browser or application will be requesting for a resource from the server. The resource would be a sensor reading like temperature, humidity, heartbeat, etc. 

For complete explanation of the source code and the demo please go through the video:


CoAP can be developed with many programming or scripting languages like:

  1. Python
  2. Node JS
  3. Contiki OS

In this article, I will be writing or explaining the source code of CoAP using Node JS and this can be demonstrated with a plugin name called Cu Plugin for Chrome Browser. There are many CoAP client available like coap, libcoap, etc in Linux OS and Cu Plugin being a easier and common approach for a client. 

You can refer the complete

This program first starts the CoAP Server and accept only the JSON format headers, else it will throw the error number '4.06'. 

Based on the request URL (req.url), the incoming requests will be handled by the server and responded with json based sensor values namely: for example, for "temperature", the server respond with {'temperature':988}. The values generated her is baaed on a random integer, in case of real sensor attached to the sensor, it can send those information as well. 

Here is the source code of the CoAP program.  The name of the file is coap.js 

var coap = require('coap');

function randomInt(min,max) {

return (Math.floor(Math.random()*(max-min) + min));
}

var portNumber=5683;
coap.createServer(function (req,res) {
console.info('CoAP device got a request from %s', req.url);
if(req.headers['Accept'] != 'application/json') {
res.code='4.06';
return res.end();
}
switch(req.url) {
case "/co2":
displayOutput(res, {'Co2':randomInt(0,1000)});
break;
case "/temperature":
displayOutput(res, {'Temperature':randomInt(-10,50)});
break;
case "/humidity":
displayOutput(res, {'Humidity':randomInt(0,100)});
break;
default:
displayOutput(res);
}
}).listen(portNumber);
console.log('CoAP Server is started at port Number 5683');

function displayOutput (res,content) {
if(content) {
res.setOption('Content-Format','application/json');
res.code='2.05';
res.end (JSON.stringify(content));
} else {
res.code='4.04';
res.end();
}
}
//End of Program
To install the packages in Linux, here is the command
$ sudo apt update
$ sudo apt install nodejs npm
$ npm install coap
The above program can be run using the command 
$ node coap.js 
The request are  
coap://localhost:5683/co2
coap://localhost:5683/temperature
coap://localhost:5683/humidity

The following will be the output
{'Co2':899}
{'Temperature':45}
{'Humidity':67}
This will start the server and the client can browse the server through the plugin called Cu plugin in Google Chrome Browser. There is a small work around to do the customisation. Please follow the video for enabling the Cu plugin in Google Chrome browser. 

Here is the output screen shot of the above request.
CoAP
CoAP Client (Cu) plugin


Comments

Popular posts from this blog

Installing ns3 in Ubuntu 22.04 | Complete Instructions

In this post, we are going to see how to install ns-3.36.1 in Ubuntu 22.04. You can follow the video for complete details Tools used in this simulation: NS3 version ns-3.36.1  OS Used: Ubuntu 22.04 LTS Installation of NS3 (ns-3.36.1) There are some changes in the ns3 installation procedure and the dependencies. So open a terminal and issue the following commands Step 1:  Prerequisites $ sudo apt update In the following packages, all the required dependencies are taken care and you can install all these packages for the complete use of ns3. $ sudo apt install g++ python3 python3-dev pkg-config sqlite3 cmake python3-setuptools git qtbase5-dev qtchooser qt5-qmake qtbase5-dev-tools gir1.2-goocanvas-2.0 python3-gi python3-gi-cairo python3-pygraphviz gir1.2-gtk-3.0 ipython3 openmpi-bin openmpi-common openmpi-doc libopenmpi-dev autoconf cvs bzr unrar gsl-bin libgsl-dev libgslcblas0 wireshark tcpdump sqlite sqlite3 libsqlite3-dev  libxml2 libxml2-dev libc6-dev libc6-dev-i386 libclang-dev llvm-

Installation of NS2 (ns-2.35) in Ubuntu 20.04

Installation of NS2 (ns-2.35) in Ubuntu 20.04 LTS Step 1: Install the basic libraries like      $] sudo apt install build-essential autoconf automake libxmu-dev Step 2: install gcc-4.8 and g++-4.8 open the file using sudo mode $] sudo nano /etc/apt/sources.list Include the following line deb http://in.archive.ubuntu.com/ubuntu bionic main universe $] sudo apt update $] sudo apt install gcc-4.8 g++-4.8 Step 3:  Unzip the ns2 packages to home folder $] tar zxvf ns-allinone-2.35.tar.gz $] cd ns-allinone-2.35/ns-2.35 Modify the following make files. ~ns-2.35/Makefile.in Change @CC@ to gcc-4.8 change @CXX@ to g++-4.8 ~nam-1.15/Makefile.in ~xgraph-12.2/Makefile.in ~otcl-1.14/Makefile.in Change in all places  @CC@ to gcc-4.8 @CPP@ or @CXX@ to g++-4.8 open the file: ~ns-2.35/linkstate/ls.h Change at the Line no 137  void eraseAll() { erase(baseMap::begin(), baseMap::end()); } to This void eraseAll() { this->erase(baseMap::begin(), baseMap::end()); } All changes made Step 4: Open a new termi

Square and Sinusoidal Waveform in 8051 Microcontroller

Waveforms in 8051 Microcontroller Square Wave To create a square wave generation using Delay. let us say we want to construct a 1khz square waveform the processor instruction cycle of 8051 is 1.085microseconds so for 1khz (1milli seconds =1/1khz), is 1ms/1.085microseconds = 921.6 (this value is set to the for loop) #include <reg51.h> void delay() { int i=0; for(i=0;i<922;i++) } void main() { P0=0xff; delay(); P0=0x00; delay(); } Sine Wave generation Since sine wave is plotted in a digital device the number of samples determines the smoothness, hence in this case, more the samples, smoother is the waveform. so a lookup table is been created to get the samples. in the following examples, there are totally 36 samples are taken, starting from 0 degrees to 360 degrees with a step of 10 degrees Degrees A = 5 (1+Sin theta) Where 5 is the full scale voltage DAC = 25.6 * A 0 5 128 30 7.5 192 60 9.3 239 90 10 256 etc…like this we need to calculate for 13 samples  with a ste