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   1 /**
   2  * Copyright (c) 2010-2022 Contributors to the openHAB project
   3  *
   4  * See the NOTICE file(s) distributed with this work for additional
   5  * information.
   6  *
   7  * This program and the accompanying materials are made available under the
   8  * terms of the Eclipse Public License 2.0 which is available at
   9  * http://www.eclipse.org/legal/epl-2.0
  10  *
  11  * SPDX-License-Identifier: EPL-2.0
  12  */
  13 package org.openhab.binding.network.internal.dhcp;
  14
  15 import java.net.SocketException;
  16 import java.util.Map;
  17 import java.util.TreeMap;
  18
  19 import org.eclipse.jdt.annotation.NonNullByDefault;
  20 import org.eclipse.jdt.annotation.Nullable;
  21 import org.slf4j.Logger;
  22 import org.slf4j.LoggerFactory;
  23
  24 /**
  25  * A singleton. IPRequestReceivedCallback objects can register and unregister.
  26  * If the first one is registered and there is no singleton instance, an instance will be created and the
  27  * receiver thread will be started. If the last IPRequestReceivedCallback is removed, the thread will be stopped
  28  * after the receive socket is closed.
  29  * IPRequestReceivedCallback will be called for the address that is registered and matches the
  30  * DHO_DHCP_REQUESTED_ADDRESS address field.
  31  *
  32  * @author David Graeff - Initial contribution
  33  */
  34 @NonNullByDefault
  35 public class DHCPListenService {
  36     static @Nullable DHCPPacketListenerServer instance;
  37     static Map<String, IPRequestReceivedCallback> registeredListeners = new TreeMap<>();
  38     static Logger logger = LoggerFactory.getLogger(DHCPListenService.class);
  39
  40     @SuppressWarnings({ "null", "unused" })
  41     public static synchronized DHCPPacketListenerServer register(String hostAddress,
  42             IPRequestReceivedCallback dhcpListener) throws SocketException {
  43         DHCPPacketListenerServer instance = DHCPListenService.instance;
  44         if (instance == null) {
  45             instance = new DHCPPacketListenerServer((String ipAddress) -> {
  46                 IPRequestReceivedCallback listener = registeredListeners.get(ipAddress);
  47                 if (listener != null) {
  48                     listener.dhcpRequestReceived(ipAddress);
  49                 } else {
  50                     logger.trace("DHCP request for unknown address: {}", ipAddress);
  51                 }
  52             });
  53             DHCPListenService.instance = instance;
  54             instance.start();
  55         }
  56         synchronized (registeredListeners) {
  57             registeredListeners.put(hostAddress, dhcpListener);
  58         }
  59         return instance;
  60     }
  61
  62     public static void unregister(String hostAddress) {
  63         synchronized (registeredListeners) {
  64             registeredListeners.remove(hostAddress);
  65             if (!registeredListeners.isEmpty()) {
  66                 return;
  67             }
  68         }
  69
  70         final DHCPPacketListenerServer instance = DHCPListenService.instance;
  71         if (instance != null) {
  72             instance.close();
  73         }
  74         DHCPListenService.instance = null;
  75     }
  76 }