There are two excellent howtos on how to setup a bacula server and remote client(s) at digitalocean:
https://www.digitalocean.com/community/tutorials/how-to-install-bacula-server-on-ubuntu-14-04
https://www.digitalocean.com/community/tutorials/how-to-back-up-an-ubuntu-14-04-server-with-bacula

But as it tailored to be used in a digitalocean vps environment it lacks a firewall setup/issues.

On the server the ports 9102 and 9103 should be opened and on the client port 9102.
The client talks to the server and the server talks to the client (or so it seems)