I would like to know if is there any way of knowing who are the current connected subscribers to a specific topic? (mybe by thire ip's or any other identificiation)
You can use the management API, look at TopicControl to find the subscriptions and you can disconnect via JmsServerControl.
beside of that how could I avoid an unknown subscriber to connect my Topic?
or mybe there is a way of auth a subscriber who wish to connect to a Topic?
Have you read the user manual, there is a full section on security