Edge Gateway triggering alerts

To run the Edge Gateway code, the prerequisites are given as follows:

• Download the code from GitHub. Samples are in the chapter 2 Iiot-Sample 1 project.
• The Edge Gateway code is in the folder iiot-edge-gateway.
• NPM and Node should be installed.
• To install the application, issue the following command:

npm install

• For this example, we are using socksjs as the client library for WebSocket. SocksJS provides the fallback between WebSockets and HTTP/HTTPS.
• Stomp protocol to send the data between the cloud and gateway.

• Details of the sample Edge Gateway is given in the following example. The code essentially reads data from a simulated sensor, in this case a .csv file, and then establishes connection to the server using the WebSocket protocol: 

//include the stomp package and socks js

var Stomp = require('webstomp-client');
var SockJS = require('sockjs-client');

// reading CSV files using 
var csv=require('fast-csv'),
   fs = require("fs");


// open the connection to the WebSocket end point. 
var socket = new SockJS('http://localhost:5074/iiot-sample-WebSocket');
//create a stomp session 
var stompClient = Stomp.over(socket);

• Read from the CSV file and check for any deviation. Check for any reading above 50.
• If so, trigger an alert to the cloud service API.
• We will add security in the later chapters. This sample does not add authentication:

function readFromSensorDataAndCheckforAnomalies(){

  var stream = fs.createReadStream("sensordata.csv");
 
  csv
   .fromStream(stream, {headers : true})
   .validate(function(data){
       return data.temp <= 50; //all reading under  50 are valid
   })
   .on("data-invalid", function(data){
        

        var alertData = JSON.stringify({'alertsUuid':'alertsid'+ new Date(),
                      'severity':1,
                      'alertName':'HighTemprateAlert',
                      'alertInfo':'Temperature Value:' + data.temp });
       stompClient.send("/app/createAlert",alertData,{});
   })
   .on("data", function(data){
       console.log(data);
   })
   .on("end", function(){
       console.log("done");
  

• Sample temperature data given in the following example should trigger two alerts to the cloud and it is contained in the sensordata.csv:

id,temp
1,5
2,50
3,400
4,20
5,50
6,70

• The JSON structure of the alerts that gets generated is given in the following example:

{
"alertsUuid": "alertsId",
"severity": 1,
"alertName": "HighTemperature Alert",
"alertInfo": "Temperature Value"
}

• Establish connection to the cloud service for generating alerts by subscribing to the alertCreated topic.
• Sending the alerts to the alerts service in the cloud is given as following (essentially we publish any WebSocket message to the cloud):
  

function createAlertInCloud() {

  // Connect to cloud using WebSocket and create alerts
  
    stompClient.connect({}, function (frame) {
        //setConnected(true);
        console.log('Connected: ' + frame);
        stompClient.subscribe('/topic/alertCreated', function (alert) {
             console.log('gotResponse from CloudService: ' + alert);
        });
        readFromSensorDataAndCheckforAnomalies();
        
    });
};


createAlertInCloud();

• Run the node idiot-edge.js to see the result. It should send two alerts to the server:

node iiot-edge.js