How to kill server when seeing “EADDRINUSE: address already in use”

A tutorial on how to kill the process manually when “EADDRINUSE” happens on Mac/Linux and Windows.

The Problem

When trying to restart a Node application, the previous one did not shut down properly, and you may see a “listen EADDRINUSE: address already in use” error such as:

The cause behind this issue

The reason behind this is that

process.on('exit', ...) isn't called when the process crashes or is killed. It is only called when the event loop ends, and since server.close() sort of ends the event loop (it still has to wait for currently running stacks here and there) it makes no sense to put that inside the exit event.

Solution

The proper fix for the application would be

• On crash, do process.on('uncaughtException', ..)
• And on kill do process.on('SIGTERM', ..)

When this EADDRINUSE issue has already happened, in order to resolve it, you need to kill the process manually. In order to do that, you need to find the process id (PID) of the process. You know the process is occupying a particular port on your machine or server.

Kill the process manually

For Mac/Linux

To find the process id (PID) associated with the port

⇒ lsof -i tcp:3000 
COMMAND PID   USER  FD  TYPE DEVICE             SIZE/OFF NODE NAME 
node    44475 chen5 31u IPv4 0x8b1721168764e4bf 0t0 TCP *:strexec-s (LISTEN)

Then to kill the process

kill -9 44475

Use -9 option to make sure the process dies immediately

If you get permissions errors, you may need to use the sudo keyword, for example:

sudo kill -9 44475

For Windows

Solution 1: Task Manager

Open the Task Manager application (taskman.exe), from either the Processes or Services tab sort by the PID column. To display the PID column, right-click the header row and select PID from the list. Right-click the process you want to stop and select End task.

Solution 2: Use Command prompt

Open a CMD window in Administrator mode by navigating to Start > Run > type cmd > right-click Command Prompt, then select Run as administrator.

Use the netstat command lists all the active ports. The -a switch displays all ports in use, not just the ports associated with the current user. The -n option stops a hostname lookup (which takes a long time). The -o option lists the process ID that is responsible for the port activity. The findstr command matches the header row that contains the PID string, and the port you are looking for, in a port format with the preceding colon, is :3000.

C:\Users\admin>netstat -ano|findstr "PID :3000" 
Proto Local Address Foreign Address State PID 
TCP 0.0.0.0:3000 0.0.0.0:0 LISTENING 18264

To kill this process (the /f is force):

taskkill /pid 18264 /f

Enjoy!

And that’s about it. Thanks for reading

Level Up Coding

Thanks for being a part of our community! Level Up is transforming tech recruiting. Find your perfect job at the best companies.