For 127.0.0.1 it will try to connect and fail, either right away or on timeout depending on the on-box firewall setup. For 0.0.0.0 it won't even try to connect

For 127.0.0.1 it will try to connect and fail, either right away or on timeout depending on the on-box firewall setup. For 0.0.0.0 it won't even try to connect (or fail instantly depending on how you look at it).