I can't kill a port process

kill -9 4469 

or

 fuser -k -n tcp 3000

3000 is the port number

or Use killport command :

wget https://raw.github.com/abdennour/miscs.sh/master/killport
killport 3000 

I know this is old, but I found this useful to me as well. Combining the lsof command from your question and the kill-9 from Abdennour TOUMI's answer into a much simpler and quicker one-line command would give the following:

kill -9 `lsof -t i:3000`

Inside of the two bactick (`) keys, you have the lsof -t i:3000 command from before, which gets the process on the port 3000. Then, the kill -9 command kills that process.