This Ruby example lists the hosts.

# Get the reference to the root of the services tree:
system_service = connection.system_service

# Get the reference to the service that manages the
# collection of hosts:
host_service = system_service.hosts_service

# Retrieve the list of hosts and for each one
# print its name:
host = host_service.list
host.each do |host|
  puts host.name
end

In an environment with only one attached host (Atlantic) the example outputs:

Atlantic

For more information, see http://www.rubydoc.info/gems/ovirt-engine-sdk/OvirtSDK4/HostsService:list.