Find (and kill) process locking port 3000 on Mac

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
   

Find:

sudo lsof -i :3000

Kill:

kill -9 <PID>

Quick and easiest solution:

kill -9 $(lsof -ti:3000)

For multiple ports:

kill -9 $(lsof -ti:3000,3001)

#3000 is the port to be freed

Kill multiple ports with single line command:

kill -9 $(lsof -ti:3000,3001)

#here multiple ports 3000 and 3001 are the ports to be freed

lsof -ti:3000

If the prot is occupied, thie above command will return something like this: 82500 (Process ID)

lsof -ti:3001

82499

lsof -ti:3001,3000

82499 82500

kill -9 $(lsof -ti:3001,3000)

Terminates both 82499 and 82500 processes in a single command.

For using this in package.json scripts:

"scripts": {
   "start": "kill -9 $(lsof -ti:3000,3001) && npm start"
}

In terminal you can use:

npm run start

Nothing above worked for me. Anyone else with my experience could try the following (worked for me):

Run:

lsof -i :3000 (where 3000 is your current port in use)

then check status of the reported PID :

ps ax | grep <PID>

finally, "begone with it":

kill -QUIT <PID>