JGroups is a toolkit for reliable multicast communication. (Note that
this doesn't necessarily mean IP Multicast, JGroups can also use
transports such as TCP). It can be used to create groups of processes
whose members can send messages to each other.

The main features include

* Group creation and deletion. Group members can be spread across LANs or WANs
* Joining and leaving of groups
* Membership detection and notification about joined/left/crashed members
* Detection and removal of crashed members
* Sending and receiving of member-to-group messages (point-to-multipoint)
* Sending and receiving of member-to-member messages (point-to-point)