How many times have you looked up "That Port Is Already In Use"?
It's an easy fix: Find the PID of the process running on your PORT, kill that process
[sudo] lsof -i :[PORT] kill -9 <PID>
LSOF And KILL In Detail
Understanding what exactly you just did to kill a process may help save you a Stack Overflow search for "That Port Is Already In Use"
[sudo] lsof -i :[PORT]
List the files of whose Internet address matches -i , but in this case we are just matching to a PORT number
kill -9 <PID>
kill the process with the specified PID, send a kill signal -9 To send a termination signal, use -15