Service and Topology Tracking

Users can subscribe for contents of and changes to the global address binding table.
They receive an event at each change matching the range indicated in the subscription.
There is a match when an bound/unbound instance or range overlaps with range subscribed for.
Received events contain the bound/unbound socket’s service address and socket address.

Cluster topology tracking is a special case of service tracking, also based on the binding table contents
Peer node availability, as seen from the own node, is represented by the built-in service type 0.
Cluster connectivity tracking is also possible by subscribing for availability of individual links, using the built-in service type 2.
Using these mechanisms, and by connecting to other cluster nodes's topology servers, it is possible for a user to build and track the overall connectivity matrix of the whole cluster.

Communication group members can optionally subscribe for join/leave/close/ /crash/lost-contact events for other group members.
Membership events are received in a member socket in the form of out-of-band empty messages.
Event order is guaranteed, - a join event always arrives before the first message from the new member, - a leave event always arrive after the last message from the leaving member.