Find (and kill) process locking port 3000 on Mac

Question

How do I find (and kill) processes that listen to/use my TCP ports? I'm on macOS.

Sometimes, after a crash or some bug, my Rails app is locking port 3000. I can't find it using ps -ef...

When running

rails server 

I get

Address already in use - bind(2) (Errno::EADDRINUSE) 

The same issue happens when stopping Node.js process. Even after the process is stopped and the app stops running, port 3000 is locked. When starting the app again, getting

Address already in use (Errno::EADDRINUSE) 

Answer 1

1. You can try netstat

    netstat -vanp tcp | grep 3000 

2. For macOS El Capitan and newer (or if your netstat doesn't support -p), use lsof

    lsof -i tcp:3000  

3. For Centos 7 use:

    netstat -vanp --tcp | grep 3000 

Answer 2

Find:

sudo lsof -i :3000 

Kill:

kill -9 <PID> 

PLEASE NOTE: -9 kills the process immediately, and gives it no chance of cleaning up after itself. This may cause problems. Consider using -15 (TERM) or -3 (QUIT) for a softer termination which allows the process to clean up after itself.