"JXTA defines several types of resources; for example, network nodes (peers), peer groups, communication channels, pieces of data, and so forth.
Every node in a JXTA network is a peer. Every peer connected to JXTA network should have a unique identity, called a Peer ID. The peer ID will be dynamically (late) bound to its IP or TCP address by the JXTA network.
A peer group is a logical rather than a physical entity; it is formed by the grouping of peers sharing common interests. For example, there can be groups, one each for all the different types of music, so that music lovers can join groups according to their taste to discuss and exchange songs.
Peers are identified by their IDs in a JXTA network. Therefore, a peer group has no concern over the IP address currently used by any of its group members. This effectively hides the unreliability associated with the dynamic behavior and changing topology of interconnected networks."
This is one of the things at the time that I thought was so good about JXTA at the time. They also mention JXTA4J2ME or JXTA for J2ME.