You should try killing the process that is listening on port 80.

If using unix try this command:

sudo fuser -k 80/tcp 

You should try killing the process that is listening on port 80.

Killall will kill all the node apps running. You might not want to do that. With this command you can kill only the one app that is listening on a known port.

If using unix try this command:

sudo fuser -k 80/tcp