Jini Message Board
I orginally wanted to show the a Jini Message Board at the 8th Jini Community Meeting last December. Unfortunately the network was against us and the demo didn't work.
In order to allow others to have a look at the board I decided to create an online demo of the Message Board that can be launched using Java Webstart. The demo is available at http://conferences.jini.org. The conferences project website contains a link that allows you to webstart the board. You don't have to login to run the demo!
Why is it a Jini Message Board? The board currently uses two Jini features: RemoteEvents and Leasing. RemoteEvents (events sent to remote computers) are used to send new messages to all users that are currently running the board. Thereby you immediately obtain messages sent by others.
Leasing is used in order to automatically stop sending events to users who have closed their board or aren't reachable due to a network failure. I.e. users obtain a lease for RemoteEvents from the server that lasts e.g. five minutes. If they don't renew the release, the server will stop sending events to them. This is neccessary, because the explicit removal of remote event listeners may fail due to network failures - keeping the server to send events to this listener inifitely when leasing wouldn't be used.
Thought Jini is about 4-5 years old it is currently most often used in larger scale distributed systems, often in conjunction with JavaSpaces. The use of Jini over the internet and on the desktop is still rarely explored. The board is an attempt to try to explore both fields and gain experience for further projects.
One of the next steps will definitely be to setup of a public Lookup service where clients can access services from the internet. The community is currently discussing how the LUS can be secured, which is not a trivial problem, but one that can be solved with the capabilities Jini provides.