@startuml
skinparam shadowing false
title Master registration (every 5 min)

participant "Master\netmaster.net:27950" as master
participant "etrelay\nfront :27960" as relay
participant "ET server\n(via wg + nginx)" as et

== Liveness probe (dedicated ephemeral socket) ==
relay -> et : getinfo etrelay
et --> relay : infoResponse
note right of relay : up: send heartbeat\nno answer x3: skip (or flatline once)

== Heartbeat (public socket) ==
relay -> master : heartbeat EnemyTerritory-1\nsource = front:27960

== Master checks: handled like any client ==
master -> relay : getChallenge\nto front:27960
relay -> relay : new session for master:27950
relay -> et : getChallenge
et --> relay : challengeResponse
relay --> master : challengeResponse\nsource = front:27960
master -> relay : getInfo
relay -> et : getInfo
et --> relay : infoResponse (hostname, map, players)
relay --> master : infoResponse\nsource = front:27960
note left of master : lists <front-ip>:27960
@enduml