TransientTransactionError while starting mongodb - node.js

Question

I am not able to solve the mongodb connection problem. I am getting the error below on starting node app.
Here is my mongoose connection code.
var mongoose = require('mongoose');
mongoose.Promise = global.Promise;
mongoose.connect(process.env.MONGODB_URI || 'mongodb://127.0.0.1:27017/ml').then(
() => { console.log('Connected to mongodb!') },
err => { console.log('Failed to connect to mongodb'); console.log(err); }
);
module.exports = {mongoose};
Here is the error.
Started up at port 80
Failed to connect to mongodb
{ MongoNetworkError: failed to connect to server [10.160.0.2:27017] on first connect [MongoNetworkError: connect ECONNREFUSED 10.160.0.2:27017]
at Pool.<anonymous> (/home/shivamsharma_btp2/mlsever/magguland/node_modules/mongodb-core/lib/topologies/server.js:564:11)
at Pool.emit (events.js:189:13)
at Connection.<anonymous> (/home/shivamsharma_btp2/mlsever/magguland/node_modules/mongodb-core/lib/connection/pool.js:317:12)
at Object.onceWrapper (events.js:277:13)
at Connection.emit (events.js:189:13)
at Socket.<anonymous> (/home/shivamsharma_btp2/mlsever/magguland/node_modules/mongodb-core/lib/connection/connection.js:246:50)
at Object.onceWrapper (events.js:277:13)
at Socket.emit (events.js:189:13)
at emitErrorNT (internal/streams/destroy.js:82:8)
at emitErrorAndCloseNT (internal/streams/destroy.js:50:3)
at process._tickCallback (internal/process/next_tick.js:63:19)
name: 'MongoNetworkError',
errorLabels: [ 'TransientTransactionError' ],
[Symbol(mongoErrorContextSymbol)]: {} }
Here are firewall rules of my google cloud app.

Answer 1

Got solution!
Use sudo before the command to start server.