subscribe-event-ws.js

/**
 * Part of a course on Hyperledger Fabric: 
 * http://ACloudFan.com
 * 
 * Tested with Composer 0.20.5
 * 
 * Pre-Requisites
 * 1. Launch Fabric - Deploy Aircraft v8
 * 2. Launch REST Server
 * 
 * Uses the NPM library for websockets
 * https://www.npmjs.com/package/websocket
 * 
 * Demonstrates how applications can subscribe to the events 
 * published by the REST server
 * 
 * 1. Setup the websocket library (npm install websocket --save) ... already done
 * 2. Create a websocket client object
 * 
 */
var counter=0;

 // #1 Need to use the websocket library
var WebSocketClient = require('websocket').client;

// #2 Create a WS Client
var client = new WebSocketClient();

// #3 Setup the WS connection failure listener
client.on('connectFailed', function(error) {
    console.log('Connect Error: ' + error.toString());
});

// #4 Setup the on connection listener
client.on('connect', (connection)=>{
    console.log("Connected to REST-Server over WS protocol!!!");

    // #5 Subscribe to messages received on WS
    connection.on('message',(msg)=>{
        var event = JSON.parse(msg.utf8Data);

        // #6 Filter the events
        switch(event.$class){
            case    'org.acme.airline.flight.FlightCreated':
                    counter++;
                    console.log('Event#', counter);
                    
                    processFlightCreatedEvent(event);
                    break;
            default:
            console.log("Ignored event: ", event.$class);
        }
    })
})

// #7 Call connect with URL to the REST Server
client.connect('ws://localhost:3000');



// #8 Gets called every time an event is receieved
function  processFlightCreatedEvent(event){
    console.log('Received event:')
    // Pretty printing the received JSON string
    console.log(JSON.stringify(event,null,4));
    console.log();
}