Kill process that is using paricular port

Find process id and kill it

ruby@t61:~/dev/ruby/demo$ sudo netstat -lpn | grep 3000
[sudo] password for ruby:
tcp        0      0 127.0.0.1:3000          0.0.0.0:*               LISTEN      5358/ruby     
ruby@t61:~/dev/ruby/demo$ kill -9 5358