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 specifying a port  app listen     the app runs but the web page does not load  On port 3001  app listen 3001   or any other port that is not in use  the app runs but the web page does not load   On port 2999  the app throws an error because something else is using that port  On port 3000  the app runs and the web page loads fine    I know that Express apps default to port 3000  But strangely  my app only runs when I explicitly make it run on port 3000  app listen 3000     I found this on line 220 of  usr bin express   app set   port    process env PORT    3000     Which is doing as previously stated  setting the port to what is specified or to 3000 if nothing is specified   How could I make my app work on a different port such as 8080 or 3001   Thanks   Edit  Code Sample  Very Simple Node Express App   var express   require  express    var app   express     app get      function req  res       res send  hello world             Only works on 3000 regardless of what I set environment port to or how I set  value  in app set  port    value    app listen 3000

User · Answer

If you are using Nodemon my guess is the PORT 3000 is set in the nodemonConfig  Check if that is the case

User · Answer

The following works if you have something like this in your app js   http createServer app  listen app get  port      function        console log  Express server listening on port     app get  port           Either explicitly hardcode your code to use the port you want  like   app set  port   process env PORT    3000     This code means set your port to the environment variable PORT or if that is undefined then set it to the literal 3000   Or  use your environment to set the port  Setting it via the environment is used to help delineate between PRODUCTION and DEVELOPMENT and also a lot of Platforms as a Service use the environment to set the port according to their specs as well as internal Express configs  The following sets an environment key value pair and then launches your app     PORT 8080 node app js   In reference to your code example  you want something like this   var express   require  express    var app   express        sets port 8080 to default or unless otherwise specified in the environment app set  port   process env PORT    8080    app get      function req  res       res send  hello world            Only works on 3000 regardless of what I set environment port to or how I set     value  in app set  port    value       app listen 3000   app listen app get  port

User · Answer

Try to locate the bin www location and try to change the port number

User · Answer

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       gt        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

User · Answer

The line you found just looks for the environmental variable PORT  if it s defined it uses it  otherwise uses the default port 3000  You have to define this environmental variable first  no need to be root   export PORT 8080 node  lt your-app js gt

User · Answer

If you want to show something you re connected on 3000   var express   require  express   var app   express    app get      function  req  res      res send  Hello World        app listen 3000  function        console log  Example app listening on port 3000         I hope that will be helpful to you

User · Answer

In bin www  there is a line   var port   normalizePort process env PORT     3000      Try to modify it

User · Answer

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

User · Answer

In the lastest version of code with express-generator  4 13 1  app js is an exported module and the server is started in  bin www using app set  port   process env PORT    3001  in app js will be overridden by a similar statement in bin www  I just changed the statement in bin www

User · Answer

Make sure you are running from that folder of your application  where you have the package json

User · Answer

Just a note for Mac OS X and Linux users   If you want to run your Node   Express app on a port number lower than 1024  you have to run as the superuser   sudo PORT 80 node app js

User · Answer

Try this    PORT 8080 node app js

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

In app js  just add      process env PORT 2999    This will isolate the PORT variable to the express application

[javascript] Node.js/Express.js App Only Works on Port 3000

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