Node.js/Express.js App Only Works on Port 3000

Question

I have a Node.js/Express.js app running on my server that only works on port 3000 and I\'m trying to figure out why. Here\'s what I\'ve found:

• Without specifyi

Answer 1

Noticed this was never resolved... You likely have a firewall in front of your machine blocking those ports, or iptables is set up to prevent the use of those ports.

Try running nmap -F localhost when you run your app (install nmap if you don't have it). If it appears that you're running the app on the correct port and you can't access it via a remote browser then there is some middleware or a physical firewall that's blocking the port.

Hope this helps!

Answer 2

Try this

$ PORT=8080 node app.js

Answer 3

I am using the minimist package and the node startup arguments to control the port.

node server.js --port 4000

or

node server.js -p 4000

Inside server.js, the port can be determined by

var argv = parseArgs(process.argv.slice(2))

const port = argv.port || argv.p || 3000;
console.log(`Listening on port ${port}...`)

//....listen(port);

and it defaults to 3000 if no port is passed as an argument.

You can then use listen on the port variable.

Answer 4

I think the best way is to use dotenv package and set the port on the .env config file without to modify the file www inside the folder bin.

Just install the package with the command:

npm install dotenv

require it on your application:

require('dotenv').config()

Create a .env file in the root directory of your project, and add the port in it (for example) to listen on port 5000

PORT=5000

and that's it.

More info here

Answer 5

Answer according to current version of express

If you talk about the current version of express, if you run app.listen() to start listening without specifying port, Express will chose a random port for your application, to find out about which port it is currently running on use

app.listen(0, () => {
    console.log(app.address().port)
}

should output the port of your app. Moreover that first parameter 0 can be totally ignored but is not recommended

Answer 6

The default way to change the listening port on The Express framework is to modify the file named www in the bin folder.

There, you will find a line such as the following

var port = normalizePort(process.env.PORT || '3000');

Change the value 3000 to any port you wish.

This is valid for Express version 4.13.1