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Fix "Address Already in Use" (EADDRINUSE): Find and Kill the Process on a Port

By Ravindra Bagale, AWS & DevOps trainer · LinkedIn · Published: 16 October 2026 · Last updated: 17 October 2026

"Address already in use" (Node.js shows EADDRINUSE, Docker shows port is already allocated) means another process is already listening on that port. Find it: on Linux run sudo ss -ltnp | grep :8080, on Mac lsof -i :8080, and on Windows netstat -ano | findstr :8080. Then stop that process the proper way (systemctl stop, docker stop, or Ctrl+C), or run your app on a different port.

sudo ss -ltnp | grep :8080          # Linux: who listens on 8080?
lsof -i :8080                       # Mac (and Linux)
docker ps --filter "publish=8080"   # is it a container?
sudo systemctl stop jenkins         # stop a service properly
kill 23456                          # or stop one process by PID

A live example first

A student installs Jenkins on an Ubuntu EC2 instance, then tries to start a Spring Boot app:

***************************
APPLICATION FAILED TO START
***************************
Description:
Web server failed to start. Port 8080 was already in use.

Find out who has the port:

sudo ss -ltnp | grep :8080

LISTEN 0  50  *:8080  *:*  users:(("java",pid=1187,fd=8))

It is a Java process, PID 1187. Which one?

ps -o pid,user,cmd -p 1187

  PID USER     CMD
 1187 jenkins  /usr/bin/java -Djava.awt.headless=true -jar /usr/share/java/jenkins.war --httpPort=8080

It is Jenkins, which also uses port 8080 by default. Killing it would only work until the next reboot. Better to give one of them a new port. We start Spring Boot on 8081:

java -jar orders-api.jar --server.port=8081

Friends, always find out who owns the port before you kill anything. It may be something important.

Why does this happen?

A program "listens" on an IP address and port, for example 0.0.0.0:8080. The operating system gives each listening port to only one socket, so a second program asking for the same port gets refused. The usual reasons are:

• an old copy of your own app is still running (in another terminal, in PM2, or started with nohup),
• a service already uses that port (Jenkins and Tomcat on 8080, Apache or nginx on 80),
• a Docker container publishes that port on the host.

How do I fix it step by step?

1. Read the port number in the error.
2. Find the process with the command for your system (below).
3. Look at the program name and user to decide what it is.
4. If it is an old copy of your app, stop it.
5. If it is a system service you do not need, sudo systemctl stop <name> and sudo systemctl disable <name>.
6. If it is a container, docker stop <name>.
7. If you need both programs, change the port of one of them.
8. Start your app again and confirm with ss -ltnp.

Find the process on each system

Linux (Ubuntu, Amazon Linux, RHEL)

sudo ss -ltnp | grep :3000
sudo lsof -i :3000
sudo fuser -v 3000/tcp

sudo matters. Without it, you cannot see processes owned by other users.

macOS

lsof -nP -iTCP:3000 -sTCP:LISTEN
kill <PID>

On macOS Monterey and later, AirPlay Receiver uses port 5000 and sometimes 7000. Flask's default is 5000, so Flask users often see this error. Change the Flask port, or turn off AirPlay Receiver in System Settings.

Windows (PowerShell or Command Prompt)

netstat -ano | findstr :8080
tasklist /FI "PID eq 4321"
taskkill /PID 4321 /F

PowerShell also has Get-NetTCPConnection -LocalPort 8080 | Select-Object OwningProcess.

Docker

Error response from daemon: driver failed programming external connectivity:
Bind for 0.0.0.0:8080 failed: port is already allocated

docker ps --format "table {{.Names}}\t{{.Ports}}" | grep 8080
docker stop old-api

Or keep both and map a new host port: docker run -p 8081:8080 orders-api. Only the left number (the host port) must be free.

Change the port in your stack

Real example: the 8080 clash

Jenkins, Apache Tomcat and Spring Boot all use port 8080 by default, and they are often installed together on one practice server. That makes "Port 8080 was already in use" one of the most common errors in DevOps labs. Teams avoid it by writing down a port plan for each server and putting a reverse proxy such as nginx on port 80 or 443 in front of the apps.

Mistakes to avoid

1. Running sudo kill -9 on the first PID you see. You may stop your database or SSH.
2. Closing the terminal but leaving the app running. Check pm2 list, screen -ls or jobs.
3. Starting the app as root to use port 80. Use a reverse proxy instead, and keep the app on a high port as a normal user.
4. Opening the new port to the world. If you change the port, check the security group and only open what you really need.

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