If the Mongo server is down, the socket timeout is not applicable (it realizes it's down close to instantly). But DBPort has a constant called CONN_RETRY_TIME_MS that means DBPort will repeatedly try to connect to the unavailable server until a certain time has elapsed.

That maximum connection retry time should be configurable. The code to make it configurable is here:

https://github.com/mongodb/mongo-java-driver/pull/37