When I run docker-compose up in my Docker project it fails with the following message:

Error starting userland proxy: listen tcp 0.0.0.0:3000: bind: address already in use

netstat -pna | grep 3000

shows this:

tcp        0      0 0.0.0.0:3000            0.0.0.0:*               LISTEN      -  

I've already tried docker-compose down, but it doesn't help.

This helped me:

docker-compose down  # Stop container on current dir if there is a docker-compose.yml
docker rm -fv $(docker ps -aq)  # Remove all containers
sudo lsof -i -P -n | grep <port number>  # List who's using the port

and then: kill -9 <process id> (macOS) or sudo kill <process id> (Linux).

Source: comment by user Rub21.