Express: app.listen([port[, host[, backlog]]][, callback]): Listen application on this port

app.listen([port[, host[, backlog]]][, callback])

Binds and listens for the connection at specific port.

app.listen(3000, () => {console.log("Application started in port 3000")});

index.js

var express = require('express')

var app = express()

app.get('/', function (req, res) {
  res.send('Hello World');
});

app.listen(3000, () => {console.log("Application started in port 3000")});

Run index.js, and open the url ‘http://localhost:3000/’ in browser.

If you omit the port number or assign port to 0, then operating system will assign a randomly unused port.

index.js

var express = require('express')

var app = express()

app.get('/', function (req, res) {
  res.send('Hello World');
});

var listener = app.listen(() => {console.log('Application started on port ' + listener.address().port);});

When I ran first time, I seen below message in console.

Application started on port 5361

When I ran second time, I seen below message in console.

Application started on port 5364

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