This post goes over how to fix the error Address already in use (EADDRINUSE).

Problem

Did you encounter the error when starting a server?

> Error: Address already in use
> Error: listen EADDRINUSE

This happens because the port is already bound to a server.

There are 2 things you can do:

1. Start your server on a different port, or
2. Free the port by killing the process associated with it.

Warning: If you choose the 2nd option, make sure you’re not killing anything important.

Solution

Get the pid

Use lsof to get the process id or pid associated with the port:

lsof -ti :$PORT

Replace $PORT with the port number.

Kill the pid

To kill the process associated with the port:

kill $(lsof -ti :$PORT)

Replace $PORT with the port number.

There may be a scenario where you’ll need to pass the SIGKILL signal to stop and kill the process immediately:

kill -9 $(lsof -ti :$PORT)

Replace $PORT with the port number.

Use sudo if you don’t have permissions:

sudo kill -9 $(lsof -ti :$PORT)

Replace $PORT with the port number.

Unix users can accomplish the same thing with fuser:

fuser -k $PORT/tcp

Replace $PORT with the port number.