Cacher is the code snippet organizer for pro developers

Solution

Use netstat to check if port 3000 is used

$ netstat -vanp tcp | grep 3000

For macOS El Capitan and newer (or if your netstat doesn’t support -p), use lsof to check what processes are using particular port

$ sudo lsof -i tcp:3000 

For Centos 7 use

netstat -vanp --tcp | grep 3000

Reference

• Find (and kill) process locking port 3000 on Mac