Something Is Running On Port 3000 [100% Solved]

Sometimes, programs refuse to run on port 3000; it becomes unresponsive or produces an error message. Tackling this problem is tricky because you have to identify the problem and kill the program. You need this rectified as soon as possible but require the right strategy.

To stop or get rid of the “something is running on port 3000” error message, you can utilize the fuser method. For the fuser arguments, it obtains the protocol and port number. It further relays to protocol the running process information on port 3000.

Apart from the fuser method, we also have the lsof method, ss command, and netstat. Learning about all these methods is not overkill as there are situations where you will need alternatives. This article will cover these various commands and methods to fix port 3000.

Something Is Running On Port 3000

To get rid of this error message, you have to identify and kill the problem.

Below are four strategies to fix this issue. 

The Fuser Method

The fuser uses the “-k flag” to terminate and end a program. The -k flag is efficient, so you do not need to combine it with other commands. For the arguments, the fuser command attains the protocol and port number. It further relays to protocol the running process information on port 3000.

For Example,sudo fuser -k 3000/tcp

The command above will terminate the program; listening and running on port 3000 and tcp. Install the fuser on your computer with apt or yum.

 For apt; # use apt

 sudo apt install psmisc

For yum; # or use yum

 sudo yum install psmisc

Lsof Method

The acronym “lsof” represents a list of opened files. The command is most efficient when merged with the correct flag choice. It relays the PID of a program on port 3000 or any other port you wish to stop.

To terminate something is running on a port, identify the PID and then use the terminate command.

For Example;

# get the PID of the process

 sudo lsof -i:3000

# use the PID from the above command and stop the process

 sudo kill PID

In situations where the above commands do not terminate the program, apply a -9 flag. It would force-stop the program.

sudo kill -9 PID

You can combine the two commands as 

sudo kill -9 $(lsof -t -i:3000)

Observe we added “-t” to the command; it would identify and terminate the program on port 3000. If you do not have the lsof in your PC, use apt or yum to install it.

# use apt

 sudo apt install lsof

# or use yum

 sudo yum install lsof

The Netstat Command

The netstat assists the computer to identify programs operating on a port. When you merge and filter netstat with grep commands, it comes out as a grep output. Here are commands to bring programs operating on port 3000.

sudo netstat -lp | grep 3000

In this case, the flags of the netstat commands are -l and -p

 -l ; represents a listening program, and -p identifies the PID 

The above command will produce the PID; input the result into the command below to kill the program.

sudo kill -9 PID

-9 is the -k flag

Install the netstat command on your PC using APT or YUM

# use apt

 sudo apt install net-tools

# or use yum

 sudo apt install net-tools

The SS Command

 The ss method identifies running program information on Linux. When you combine and chain the ss command with grep and the port, it would produce the programs operating on it.

For Example, Input the ss command below

sudo ss -ltp | grep 3000

In this case, 

the -l flag will produce the will the listening programs.

the -t will identify the programs running on tcp.

the p shows the PID of the programs.

Copy and paste your program PID from the above command and terminate the program with the command below.

sudo kill -9 PID

How To Check If Something Is Running On Port 3000 Mac. 

If you have an app that must run on port 3000 on your Mac PC, try the lsof or netstat commands. In case it doesn’t work, try the comnand below.

Locate your dev”host-file.”

sudo nano /etc/hosts

Start your program

yarn start

The above program will work and rectify any problems with the localhost.

How To Check If Something Is Running On Port 3000 React Kill

The first solution to this issue is


lsof -i :3000

Confirm the PID from the above command

Input it into the command below

ps ax | grep <PID>

Finally, “terminate it”:

kill -QUIT <PID>

  1. You can try using the lsof command we mention above to solve this;

sudo lsof -i :3000


kill -9 <PID>

  1. The third command is not restricted to only port 3000 but can be used on any other port.

function killport() { lsof -i TCP:$1 | grep LISTEN | awk ‘{print $2}’ | xargs kill -9 } 

  • You can use the netstat command;

 netstat -vanp tcp | grep 3000

For a Centos 7 PC, use the command above. If your PC is a Mac or your netstat doesn’t accept the -p, use the lsof command

Remember we said -p identifies the PID of programs.

lsof -i tcp:3000 

In this command sequence, input the command below into the bash profile.

  •  bash_profile: findandkill() { port=$(lsof -n -i4TCP:$1 | grep LISTEN | awk ‘{ print $2 }’) kill -9 $port } alias killport=findandkill 

Then input killport 3000 

It is faster than the rest command methods. 

How To Check If Something Is Running On Port 3000 Ubuntu 

  • Use telnet command;

[user@lappie ~]$ telnet host 3000

Trying ip.adr.tld …

Connected to host (ip.addr.tld).

Escape character is ‘^]’.

SSH-2.0-OpenSSH_5.1p1 Debian-5

The above sequence of commands is a successful command.

Or you can use the command below;

nc -zw3 domain.tld 22 && echo “opened” || echo “closed”

Where -w3 represents timeout

It is essential to note that the above “telnet” command on ubuntu would only listen for TCP.

For UDP 3000 port, use the command below;

nmap -sU -p 3000

Where; nmap is remote system’s IP address -p is the port Number 

Before using the command above, identify and listen for the open port. To do that, merge the netstat and grep commands.

netstat -ntlp | grep LISTEN


nmap -A localhost -p: Port Number

And stop the port

For Example;

If mysql is operating on 3000, stop it using the command below. 

sudo service mysql stop

And then,

nmap -A localhost -p 3000

How To Check If Something Running On Port 3000 Create React App

To rectify this, you can stop the program or alter the script

“start”: “react-scripts start”


“start”: “PORT=3000 react-scripts start”

then input the “npm start” on another terminal.

1.On React command, you can use SPA.

The “npm start” method.

Using the command below


which is by default address

The default localhost is, and the port number is 3000

For Example;

If the create-react-app package is 3000 and you get something is running on port 3000error message, you may assume the port is in use. But you will observe that the program operates like it is always on the address.

To fix this, go to your project library. It is in your create react script app. Locate the command;


The npm start command identifies and terminates the start.js script.

In the start.js file editor, find the command below

const HOST = process.env.HOST || ‘’;

 and edit the command to input the default localhost

const HOST = process.env.HOST || ‘’;

 save the command and then run your app using: http://localhost:3000/   or http://127.0.01:3000

The create react can be fixed using the steps below;

  1. Build your app with npx, npm, or yarn.

For npx:

 npx create-react-app my-app

For npm

 npm create-react-app my-app

For yarn

yarn create-react-app my-app

  1. Change the directories

 cd my-app

  1. Run “start” command 

 with npm

 npm start

With yarn 

 yarn start


We discussed the different methods used to rectify the error message” something is running on port 3000. The error message might be due to an error in its localhost. You may need to merge two commands or use one command to correct the error. The fuser command does not need to be combined with other methods.