implement subscription

XIONControlPanel/Servers/ServerMultiplex.swift

@@ -31,6 +31,7 @@ class ServerMultiplex
     
     public func addServer(_ server: Server)
     {
+        server.delegate = self
         servers.append(server)
     }
     
@@ -138,3 +139,13 @@ extension ServerMultiplex
         }
     }
 }
+
+extension ServerMultiplex: ServerDelegate
+{
+    func server(_ server: any Server, deviceChangedState subjectDevice: AnyDevice) {
+        guard let device = devices.first(where: { $0.serial == subjectDevice.serial }) else { return }
+        device.state = subjectDevice.state
+        
+        delegate?.serverMultiplex(self, devicesStateChanged: [device])
+    }
+}