Websocket permission error

[qadirp]

I added these lines in my app.js

    poloniex.openWebSocket();
    poloniex.subscribe('accountNotifications');
    poloniex.on('message', (channelName, data) => {
        if (channelName === 'accountNotifications') {
            console.log(`account notifications update: ${JSON.stringify(data)}`);
        }
    })

and it is giving me errors below

    throw err; // Unhandled 'error' event
    ^

Error [ERR_UNHANDLED_ERROR]: Unhandled error. ('Permission denied.')
    at Poloniex.emit (events.js:300:17)
    at WebSocket.ws.onmessage (/var/www/html/nodepoloniex/node_modules/poloniex-api-node/lib/poloniex.js:624:25)