Until this week, my customer had Ensemble writing HL7 messages to my TCP listener, working fine on ageing physical servers (Windows Server 2003, Caché 2009). They had four app servers (app1, app2, app3 and app4) with an overarching DNS simply called "app". Ensemble was connecting to "app:port", and it somehow found whichever of the four app servers my background listener was running on, and the interface worked fine for 10+ years.