lsof -n -i TCP:8080
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
node 54762 user 23u IPv4 XXXXXXXXX 0t0 TCP 127.0.0.1:http-alt (LISTEN)
PID // is second field in the response . Then, kill that process:
kill -9 54762 // here put PID number found on the table 54762
sudo lsof -i :5955
npx kill-port 3000
sudo lsof -i <Port>
sudo kill -9 <PID>