manjaro kill port 3000

C++
kill -9 $(lsof -t -i tcp:8080)
#To list any process listening to the port 8080:
lsof -i:8080

#To kill any process listening to the port 8080:
kill $(lsof -t -i:8080)

#or more violently:
kill -9 $(lsof -t -i:8080)
Source

Also in C++: