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
/*
if you have ran a code that uses a server or server port you can easily
kill the server port, and the just created server i think, simply typing:
(ctrl + c) or (cmd + c) for MAC
*/