You'll need to forward the port from the VM to the host. An example for the default "random" range from docker is: (from http://docs.docker.io/en/latest/installation/mac/#forwarding-vm-port-range-to-host)
# vm must be powered off
for i in {49000..49900}; do
VBoxManage modifyvm "boot2docker-vm" --natpf1 "tcp-port$i,tcp,,$i,,$i";
VBoxManage modifyvm "boot2docker-vm" --natpf1 "udp-port$i,udp,,$i,,$i";
done
But if you want to forward specifically 8080:
VBoxManage modifyvm "boot2docker-vm" --natpf1 "tcp-port8080,tcp,,8080,,8080"
etc. You might want to pick a different port if you also use 8080 for testing things on your Mac itself.