Client and server nodes can be accessed through the predefined forClients() and forServers() methods of IgniteCluster. First, get the IgniteCluster:

IgniteCluster cluster = ignite.cluster();

Invoke the forClients() method of the cluster to get all client nodes:

ClusterGroup clientGroup = cluster.forClients();

Invoke the forServers() method of the cluster to get all server nodes:

ClusterGroup serverGroup = cluster.forServers();