I am a total beginner of Node.js and I am unable to connect to localhost:3000
I use the following code in VS code, hit "node app.js" in terminal, and there is no error comes out in terminal at this point.
However, as I try to access the localhost:3000, it keeps refusing: "ERR_CONNECTION_REFUSED"
I searched on the internet for solutions and tried opening ports by creating an inbound rule on security settings, turned IIS on, used 127.0.0.1 instead, and still get refused. Does anyone have any idea how to solve this?
I am using Windows 10
const http = require('http');
var server = http.createServer(
(request, response)=>{
response.end('hello');
}
);
server.listen(3000);
Here is how to fix it. Your probably try to launch your server on a used port.
// enter this command in your terminal
lsof -i:3000
// this will output the related PID (process ID). Here: 1382.
node 1382 name 21u IPv6 blabla 0t0 TCP *:3000 (LISTEN)
// kill the PID in use
kill -9 1382
//relaunch your server
node app.js
I ran it on my computer and that code works fine. I would try other ports to see if they work.
EDIT
I think the problem might be that the WebSocket connection does not go through the proxy node.js. How to authorize the connection of the WebSocket?
I have a web app hosted on a nodeJS server. On the same vm I also have a shiny serveur hosting an app. I use node to redirect traffic to port 3838 (shiny) when a somes URL are requested.
I use this code on node :
app.use('/the-shiny-app', proxy({target: 'http://localhost:3838', changeOrigin: true}));
With this setting everything works fine on the shiny app when I go on mydomain/the-shiny-app/* except when I try to run code in a code box.
When I try to run code I get this error on the chrome console :
Connection closed. Info: {"type":"close","code":4503,"reason":"The application unexpectedly exited","wasClean":true}
An example of what I mean by code box :
if I do not use node.js and I redirect the traffic (on OS level) from port 80 directly to 3838 everything works fine.
sudo iptables -A PREROUTING -t nat -p tcp --dport 80 -j REDIRECT --to-ports 3838
I do not know exactly what kind of exchange is made between the browser and the shiny server when we run code, but maybe the protocol used is blocked by node.js.
I found the problem. As Antony Gibbs said you need to setup a WebSocket upgrade. I'm using http-proxy-middleware you cans find the doc here : https://github.com/chimurai/http-proxy-middleware
I keep on getting "? Something is already running on port 3000" message in my terminal when I start up my react server when there is absolutely nothing running on my port 3000
What I have tried to solve with:
Restart the macOS.
checking my "http://localhost:3000" on chrome browser. (Nothing: This site can’t be reached)
Go to chrome://serviceworker-internals and chrome://appcache-internals, search for localhost:3000 (Nothing found)
I also tried almost every command lines I found on Google regarding this issue
I also created another express.js app, and it was successfully launch on port 3000 while React said there is something running on 3000. React on my computer just keeping thinking there is something running on port 3000.
If you are a windows user you can try using
npx kill-port 3000
in your console. I was having the same problem and it worked for me.
Not sure about MAC.
Open cmd and write this
netstat -a -o -n
You will get list of active connections then find 3000 by hitting
Cntrl + f
Copy the PID of that port and hit this command
taskkill /F /PID PID_of_port
Edit
This guide is for windows.
Kill Node.Js process from Task Manager.
Step 1: Open Task Manager by clicking ctrl+shift+delete
Step 2: Open Prcesses tab
Step 3: Search for Node.JS process and right click on that then click on End Task
Step 4: Now you can start again.
As #khurram khan suggested terminating the process may be the best option for you, This work for me on linux:
$ lsof -i tcp:3000
$ kill -9 PID
the first command should give you the PID number to enter in the second command as PID.
I had this problem on Mac and I solved by running:
npx kill-port 3000
I had stuck with this one for few hours, and the end I had found the solution
There was incorrect mapping to the local host in the hosts file and didn't had any relation to the port taken something like
10.2.224.130 localhost
Just Change it back to
127.0.0.1 localhost
Host file locations
https://www.howtogeek.com/howto/27350/beginner-geek-how-to-edit-your-hosts-file/
In case anyone comes across this and the above solutions didn't help, make sure your /etc/hosts has:
127.0.0.1 localhost
For some reason this was wiped from my hosts file and CRA's dependency for checking ports (detect-port-alt) checks localhost:[PORT] to see if it's available. If it errors out, you'll always get the "Something is already running..." error when checking a specific port but not when using a random port (since that's picked by the dependency).
kill node.js from the background processes. that would soleve the probelem. alterntively, you could restart your system
for window use this in package.json
"start": "set PORT=3006 && react-scripts start"
for Linux and MacOS
"start": "PORT=3006 react-scripts start"
This worked for me on windows pc. This one is for those are not seeing the port when you run this command netstat -a -o -n on your command prompt.
Open your command prompt in administrator mode and run this command
net stop winnat
you'll get this response:
The Windows NAT Driver service was stopped successfully.
Them you run this next:
net start winnat
then you will get this response:
The Windows NAT Driver service was started successfully.
once you do that. Start the react server and it would work. Same too if your backend server doesn't run on 3000
It's very simple. You can fix it in 2 easy steps.
Check your environment variables if there is a key/entry with name "PORT".
If found delete that entry or rename it to something else.
It turns out that some other program is using that variable. Usually when you start react-scripts it will look for an environment variable with that title PORT.
Date: Sat 07, October 2020
Windows: Microsoft Windows 10 Pro Build 19041
Node: 12.16.1
NPM: 6.14.8
Something similar was happening to me on my Windows machine. Tried a lot of things suggested here on StackOverflow and other places.
In my case, I was following a video course that was suggesting adding --script-version 1.1.5 (as illustrated below) when creating a new React app.
create-react-app app-name --scripts-version 1.1.5
Here's the package.json scripts versions:
React: 17.0.1
React DOM: 17.0.1
React Scripts: 1.1.5
After running the command npm start and typing y to try to use a different port, the terminal will stay stucked until it was canceled.
Then I created a new React app without --scripts-version 1.1.5 and after trying to running it, it was still running into Something is already running on port 3000 but after typing y, the app will run with no problem on a different port.
Here's the package.json scripts versions (when it was running successfully):
React: 17.0.1
React-Dom: 17.0.1
React-Scripts: 4.0.0
Starting with the reason you do not see anything on localhost:3000, is because there must be a proper webapp or a website/server running on that port, but the port:3000 is currently running some process, just not of a server/site/app.
This out of the way, depending on your type of OS, it is quite easy to check if there is in-fact a process on port:3000 or not. For MacOS, opening a terminal and running sudo lsof -i ':3000' will list the current process on port 3000.
Note that we need to run command as sudo or root
Once you see what process is running, note the PID and run kill -9 {PID}, which should kill the process with PID (i.e distruptive process on port:3000). Now doing a npm start should get your app built, compiled and served on localhost:3000
Mostly what might've happened is that you had a npm start running which you either interrupted, or closed in the foreground. Doing a fg in your terminal will open any background tasks, so if this opens a npm start instance, it was this process stopping your flow. You can then properly end the session making sure all processes on port:3000 are killed.
Happy coding
If you are on linux you can try
pkill -f node
to terminate the processs
The error occurs when a task is left running on the port properly killing it.
this error can occur on both ports. Your react app and your node server.
To solve this you can run the following commands.
netstat -anp tcp | grep 3000
This command in the terminal will give you the list of activities on port 3000
npx kill-port 3000
This command will kill all the running servers on port 3000.
Now if you have the same problem for your Node server. You can follow the same steps.
netstat -anp tcp | grep 5000
Then
npx kill-port 5000
You don't need the first command. it's just to list out the running activities on the port.
just change the port number for any other port number.
This is the output you get after running the commands.
I am using Git bash on windows.
For me, this works every time (macOS): sudo kill -9 $(sudo lsof -t -i:3000)
Simple and Easy solution
close your current terminal and open a new one.
If you are running it in VS Code just create a new terminal and delete the old one.
On React - you can run an already created React single-page application (SPA) by
npm start command.
That may start your locally hosting development server and runs your app at:
http://localhost:3000/ which is equivalent to: 127.0.0.1:3000 address
127.0.0.1 is the default localhost IP number while the default port number set by
create-react-app package is 3000.
When getting: “Something is already running on port 3000" failure error message you may think that the port captured by another process running on your machine but you’ll find that it is captured permanently as if it runs on 0.0.0.0:3000 address
Solution:
In your project libraries created by create-react-app script navigate to:
node_modules/react-scripts/scripts/start.js
While running npm start command - the start.js script is being called and executed
There at start.js file in you editor find the above line:
const HOST = process.env.HOST || '0.0.0.0';
and change it to:
const HOST = process.env.HOST || '127.0.0.1';
save and run your web app again at: http://localhost:3000/ or http://127.0.0.1:3000
So I've deployed my meteor app, and have it up and running on an instance.
I've used the following environment variables:
MONGO_URL='mongodb://localhost:27017/meteor'
ROOT_URL='http://<my static ip>'
PORT=3000
And I run the program using the following command:
node bundle/main.js
It prints my "Meteor is starting up" that is printed using the console.log command, and then doesn't error out, but when I navigate to http://< my static ip >:3000 in a browser, I get an ERR_CONNECTION_REFUSED result.
My open mongod terminal says it's connecting fine to the MongoDB database.
Does anyone have any ideas on how to start debugging this issue?
Thanks.
In server you don't need to run meteor application on port 3000. You can run it on port 80 if the port is not being used by any other program.
If you are using port 80 make sure port 80 is opened by the network security rules.
If you are using port 3000 or any other port you will have to make sure that port is opened by the network security rules as above. Additionally you will have to mention the IP in your url, like http://<your_ip>:<port>
I have successfully installed Node.JS and Balloons.IO chatroom on my linux based vps (with SSH). When typing curl http://mydomain.com:9191/ in the ssh command I can see the html is loaded. But, when trying to reach the same page from my browser it takes some time loading then says page could not be reached. Any idea why ?
My common diagnostic steps:
1) Check that your app is actually listening on the port it should be, you can do this with:
sudo netstat -anp | grep :9191
You should see your app listening to 0.0.0.0:9191 or your.ip.address.here:9191 if you see something like 127.0.0.1:9191, then it is only listening locally so you won't be able to reach it.
2) Ensure your firewall isn't blocking these ports, if you are using iptables you can check with:
sudo iptables --list
This will print the rules for your firewall and you can check if you port is blocked (or allowed).
3) Try connecting locally. My third step is generally to try it locally with curl, you did this step already but for other landing here you can do something like:
curl http://localhost:9191/
and see what you get back
4) Try connecting remotely. If everything above looks fine, try running a verbose curl from a remote host and see what you get:
curl -v http://mydomain.com:9191/
This will show header and body output so you can see if the remote host even responds; if it doesn't then check if the raw port is even accessable with telnet:
telnet mydomain.com 9191
which if successful will print something like:
Trying your.ip.address.here...
Connected to mydomain.com.
Escape character is '^]'.
If it fails it will just hang at Trying... if it fails then your firewall is blocking the port, your host is blocking the port, or your app isn't listening to the port. If your above tests passed then contact your host because something else may be up and you should be able to get support from them.