I'm building an application which has one online database (server) and multiple local databases (client).

The clients need to synchronize with de server. Since all queries are done through Hibernate,
I thought there might be some tool to do this for me. Does someone know a tool that can help me with this?

Multiple clients must be able to run at the same time and the server will always run.
The clients need to be able to run without internet, therefor all have a local database.
The clients will synchronize on start-up and (if possible) every few minutes.

Edit: Can I add a listener to the queries executed by Hibernate? If so I could collect these and send them using sockets.