class Player {
  public string X { get; set; }
  public string Y { get; set; }
}

var protocol = new SimpleRealmProtocol(new[] { typeof(Player) });
var service = new RealmService(protocol);
service.UserStateChanged += (s, a) => {
  var player = a.User["player"] ?? new Player();
  if (a.State == ConnectionState.Connected) service.AddEntity(player);
  if (a.State == ConnectionState.Disconnected) service.RemoveEntity(player);
};
service.Start(new IPEndPoint(IPAddress.Any, 9876));

var client = new RealmClient(protocol);
client.EntityStateChanged += (s, a) => {
  if (a.State == EntityState.Added) _realm.AddEntity(a.Entity);
  if (a.State == EntityState.Removed) _realm.RemoveEntity(a.Entity);
};
client.Connect(new IPEndPoint(IPAddress.Loopback, 9876));