[wpinet] Move network portions of wpiutil into new wpinet library (#4077)

wpinet/src/main/native/cpp/MulticastHandleManager.h

@@ -0,0 +1,26 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <memory>
+
+#include <wpi/DenseMap.h>
+#include <wpi/UidVector.h>
+
+#include "wpinet/MulticastServiceAnnouncer.h"
+#include "wpinet/MulticastServiceResolver.h"
+
+namespace wpi {
+struct MulticastHandleManager {
+  wpi::mutex mutex;
+  wpi::UidVector<int, 8> handleIds;
+  wpi::DenseMap<size_t, std::unique_ptr<wpi::MulticastServiceResolver>>
+      resolvers;
+  wpi::DenseMap<size_t, std::unique_ptr<wpi::MulticastServiceAnnouncer>>
+      announcers;
+};
+
+MulticastHandleManager& GetMulticastManager();
+}  // namespace wpi