I am not very familiar with Firebird, but I think the best approach is to use some kind of web service (RESTful?) That allows your Android client to interact with the database. This is a solution that is commonly used for most applications, since you cannot directly connect to the database with Android. This is also good from a design point of view, because your application does not depend on the underlying database itself, but rather on a web service that acts as an intermediary, which means that you can swap the database implementation without affecting the client.