Pub / Sub app

/* 
    Code a Pub/Sub app to publish 'greetings ' message. The app will also receive the greetings message from other app instances. 
    We can run 100's of these pub/sub app instances. Each of them will send a single greeting message and will receive greetings from all the other app instances. 
*/

// Include dataBridges client library package
const dBridges = require('databridges-sio-client-lib');

// Initialize dataBridges client
const dbridge = new dBridges(); 

// Replace your application key below, which you have received from dataBridges management portal.
// use environmental variables for greater security of your keys
dbridge.appkey = '____appKey______';

// Replace your authentication url below, which you have received from dataBridges management portal.
// example https://endpoint01.databridges.io/client/v1/authenticate
// use environmental variables for greater security of your keys
dbridge.auth_url = '_____URL_____';

// lets create a sessionID
const sessionID = Math.random().toString(36).substring(2, 7);
console.log('sessionID is ' + sessionID);

// Connect to dataBridges. If any runtime error it will be caught in catch().
dbridge.connect().catch((err) => {
    console.log('dataBridges Connection exception..', err.source, err.code, err.message);
});

//Bind to disconnected event, to get intimation about dataBridges network disconnection.
dbridge.connectionstate.bind("disconnected", () => {
    console.log('Disconnected from dataBridges real-time network');
});

dbridge.connectionstate.bind("connected", () => {
    console.log('Connected to dataBridges real-time network !!!');
    let helloWorld = null;
    try {
        // Subscribe to channel 'Hello-World',
        helloWorld = dbridge.channel.subscribe('Hello-World')
    } catch (err) {
        // Subscribe errors will be handled here.
        console.log('Channel subscription faced an exception: ', err.source, err.code, err.message);
    }

    // We will bind to subscription success event. On success, we will publish event messages.
    helloWorld.bind("dbridges:subscribe.success", (payload, metadata) => {
        // we can also check if the helloWorld subscription isOnline.
        if (helloWorld.isOnline()) {
            try {
                console.log('Publishing greetings ');
                helloWorld.publish('greetings', 'Greetings from ' + sessionID);

            } catch (err) {
                // Any publish error will be caught here.
                console.log('Publishing messages faced an exception:  ', err.source, err.code, err.message);
            }
        }
    });

    //Bind to the channel.event that you want to process. Here we will bind to 'greetings'
    helloWorld.bind('greetings', (payload) => {
        console.log('received greeting message : ', payload);
    });

    // Bind to Subscription failure event, to get notified if subscription to channel has been rejected by dataBridges network
    helloWorld.bind("dbridges:subscribe.fail", (payload, metadata) => {
        console.log('Channel subscription faced an exception:', payload.source, payload.code, payload.message);
    });

});