How npm start runs a server on port 8000

Question

I recently used a angular-seed folder from github for angular application development. In some previous angularjs tutorial there was a script folder and a server.js file in the angular-seed folder which had all the configuration for running the node server. So how does npm now just start running a node server and where is all the configuration of that node server?

It's in `package.json` file. See: https://github.com/angular/angular-seed/blob/master/package.json — Raghavendra, Jul 15 '14 at 05:18
I came here searching for a non-angular solution (Next.js which is basically React) and found it solution in [this answer below](https://stackoverflow.com/a/60451410/5369706). Using Next.js, at least for me, ports aren't defined in the `package.json` file; `npm run dev -- --port ####` let me specify the port. — Jason R Stevens CFA, Apr 16 '20 at 12:57

score 139 · Answer 1 · edited Mar 21 '19 at 20:41

139

We have a react application and our development machines are both mac and pc. The start command doesn't work for PC so here is how we got around it:

"start": "PORT=3001 react-scripts start",
"start-pc": "set PORT=3001&& react-scripts start",

On my mac:

npm start

On my pc:

 npm run start-pc

edited Mar 21 '19 at 20:41

Andrii Abramov

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answered Jun 10 '17 at 12:19

YeeHaw1234

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This really saved my day! I was looking for a correct to start node on port different from 3000 for Express. Thanks a lot!. By the way, start command does work on PC. It looks like this in my config `"start": "set PORT=3001 && node ./bin/www"` – Konstantin Jun 26 '17 at 04:46
Yes, I mistyped. Start does work on PC, but the syntax for setting the port is different than Mac/Linux. That's why I have 2 "start" commands. one is "start" for mac, and one is "start-pc" for my pc. – YeeHaw1234 Jun 27 '17 at 13:16

score 123 · Answer 2 · edited Mar 16 '23 at 11:55

123

To start the port correctly in your desired port use:

npm start -- --port 8000

edited Mar 16 '23 at 11:55

Juuso Ohtonen

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answered Feb 28 '20 at 12:07

theocikos

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This is exactly what I came here searching for. I am using Next.js (React) and can now run the development server on a given port; `npm run dev -- --port 8000` worked like a charm. – Jason R Stevens CFA Apr 16 '20 at 12:52
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`Something is already running on port 3000` does not work neither – Dotista Jul 13 '20 at 13:50
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This did not work for me. Module automatically starts on 3000. – BReddy Aug 25 '20 at 00:49
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Why is there an extra `--`? – Amir Heshmati Aug 31 '20 at 05:57
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On the two extra `--` there is a very good answer in this thread @AmirHeshmati https://stackoverflow.com/questions/43046885/what-does-do-when-running-an-npm-command – theocikos Oct 15 '20 at 08:29
If this doesn't work for you (as it did not work for me), try the solution suggested below, namely: PORT 8000 npm start – Andrew Einhorn Jul 17 '21 at 16:20
This command works for me. – Sabbir Sobhani Dec 21 '21 at 10:48

score 113 · Answer 3 · edited Jan 28 '20 at 10:00

113

To change the port

npm start --port 8000

edited Jan 28 '20 at 10:00

MANISH KUMAR CHOUDHARY

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answered Dec 29 '18 at 03:52

Kotireddy

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This didn't work but this did `npm start -- --port 8000` – root Sep 26 '22 at 10:12

Mritunjay · Accepted Answer · 2017-01-12T08:21:44.777

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If you will look at package.json file.

you will see something like this

 "start": "http-server -a localhost -p 8000"

This tells start a http-server at address of localhost on port 8000

http-server is a node-module.

Update:- Including comment by @Usman, ideally it should be present in your package.json but if it's not present you can include it in scripts section.

edited Jan 12 '17 at 08:21

answered Jul 15 '14 at 05:20

Mritunjay

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I couldn't find this in my package.json, however adding this under the "scripts": {} section worked for me. – Usman Jan 12 '17 at 08:05
@Usman Ideally it should be there in your `package.json`, but if not there you can always add it. Updated the answer, thanks for pointing it. – Mritunjay Jan 12 '17 at 08:23
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you just start some http server, but not react-scripts. PORT=3001 react-scripts start solves the problem – Ilya Khudyakov Oct 21 '19 at 19:25
I think in newer versions of npm it's located in "launch.json". – Karis Sr. Dec 18 '21 at 10:08

score 78 · Answer 5 · edited Feb 24 '20 at 05:24

78

You can change the port in the console by running the following on Windows:

SET PORT=8000

For Mac, Linux or Windows WSL use the following:

export PORT=8000

The export sets the environment variable for the current shell and all child processes like npm that might use it.

If you want the environment variable to be set just for the npm process, precede the command with the environment variable like this (on Mac and Linux and Windows WSL):

PORT=8000 npm run start

edited Feb 24 '20 at 05:24

datashaman

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answered Jun 14 '17 at 11:42

Skylin R

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This is much simpler for temporarily testing things out. Thanks! – sbbs Aug 07 '17 at 13:36
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I just specify it as part of the start command when I'm already running other projects on 'default' ports. `PORT= npm start` – Drew Reese Mar 23 '18 at 17:49
This is what worked for me perfectly – Koushik Das May 21 '22 at 10:30

Sehrish Waheed · Answer 6 · 2022-04-13T05:57:28.957

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npm run dev -- --port 3001

npm run on another port in cmd

edited Apr 13 '22 at 05:57

answered Apr 12 '22 at 08:30

Sehrish Waheed

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score 6 · Answer 7 · answered Nov 17 '21 at 04:57

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change "start": "react-scripts start", to "start": "set PORT=3001 && react-scripts start",

answered Nov 17 '21 at 04:57

Dinesh M

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score 6 · Answer 8 · answered Dec 01 '21 at 20:31

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Or simply in the terminal

set port=5500 && npm start

answered Dec 01 '21 at 20:31

Ashish Saini

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score 2 · Answer 9 · answered Nov 17 '20 at 11:37

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npm start -- --port "port number"

answered Nov 17 '20 at 11:37

Ashutosh Singh

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score 2 · Answer 10 · answered Dec 02 '21 at 16:55

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The solution which will work on every machine, let it be MAC, Window, Linux or any other, just specify the port where you want to run. In your package.json do this :

 "start": "export PORT=3001 && react-scripts start "

answered Dec 02 '21 at 16:55

Soumil Khandelwal

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score 1 · Answer 11 · edited Dec 27 '22 at 17:47

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npm run start -- -p 8000

8000 is port number you can change your port number

edited Dec 27 '22 at 17:47

Mechanic

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answered Feb 13 '22 at 07:00

Shihab Uddin Shakil

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score 0 · Answer 12 · answered Dec 04 '21 at 09:54

0

npm start --port 8000 does not work. You should write command like this.

ng serve --port 8000

answered Dec 04 '21 at 09:54

ibrahim

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score 0 · Answer 13 · answered Sep 14 '22 at 17:20

(For those still suffering despite trying all the answers.)

Here is a quick fix that should not be used in production!

Just forward the source port to the target one that you need. Open another shell and tap this command:

socat tcp-listen:8000,reuseaddr,fork tcp:192.168.1.48:3000

In this example; 3000 is the port of the server and 8000 the port you want to forward to (or receive from to be precise)

Enjoy!

How npm start runs a server on port 8000

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