Forge Networked Server MySQL Connection

Apologies if this has already been asked or answered here, but I searched and couldn't find anything.

I am using forge and have created two servers (with digital ocean), on one of the servers I would like to host some sites, the other I would like to use as a dedicated mysql database (which the sites on the other server connect to).

I have ticked the network box for both servers and thought this would allow me to connect to the mysql database using the server ip but it gives a connection refused error.

Has anyone got any experience with using this setup on forge? Is it possible to do this?