The gossip daemon is a process with which newly created JChannels, which use gossiping, register. A registration request containing the group name and the channel's address is sent to the gossip daemon periodically. Therefore, the daemon can be queried for all member addresses of a certain group. When a registration for a certain member is not renewed within a certain period of time, it becomes stale and will be removed by gossip. This tries to account for crashed members. When a member leaves the group, it will unregister with the gossip daemon.
The gossip daemon is implemented in JavaGroups.JavaStack.GossipServer. It is started given a port as follows (the port argument is optional, default port is 12001, host on which it is started is janet):
GossipServer -port 7879
The PING layer uses class JavaGroups.JavaStack.GossipClient to periodically register with the gossip daemon. It creates an instance of the client and starts it when the group is joined and stops it when the group is left. The gossip client periodically registers with the gossip daemon as long as it is member of the group and unregisters when it leaves the group. The PING layer has to know the address and port of the gossip daemon, which is done using arguments to property PING (using the above example of gossip daemon):
"...:PING(gossip_host=janet.cs.cornell.edu;gossip_port=7879):..."
If PING is parameterized with the gossip daemon's address and port, then gossiping is automatically enabled, otherwise it is disabled. If only 1 parameter is given, gossiping will be disabled !