Centos VM with Docker getting host unreachable when trying to connect to itself

FYI, I resolved the problem on centos by using the default "bridged" containers provided by Docker, but adding the following to my firewalld configuration:

firewall-cmd --permanent --zone=trusted --add-interface=docker0
firewall-cmd --reload
service firewalld restart

You might also need to open up a port to allow external communication, like so:

firewall-cmd --zone=public --add-port=8080/tcp --permanent