INT-4366: Fix MulticastSendingMH race condition

JIRA: https://jira.spring.io/browse/INT-4366

The `MulticastSendingMessageHandler.getSocket()` doesn't guard around
`this.multicastSocket` property causing `NPE` and other inconsistency
in the multi-threaded environment

* Make the whole `MulticastSendingMessageHandler.getSocket()` as
`synchronized` like it is with the super method
* Reuse `closeSocketIfNeeded()` in the
`UnicastSendingMessageHandler.handleMessageInternal()`
* Fix type in the `UnicastSendingMessageHandler` logging message
* Fix `UdpChannelAdapterTests` for missed `BeanFactory` for the SpEL
and also `MulticastSendingMessageHandler.stop()` in one missed places

**Cherry-pick to 4.3.x**

spring-integration-ip/src/main/java/org/springframework/integration/ip/udp/MulticastSendingMessageHandler.java

@@ -125,13 +125,11 @@ public class MulticastSendingMessageHandler extends UnicastSendingMessageHandler
 	}
 
 	@Override
-	protected DatagramSocket getSocket() throws IOException {
-		if (this.getTheSocket() == null) {
-			synchronized (this) {
-				createSocket();
-			}
+	protected synchronized DatagramSocket getSocket() throws IOException {
+		if (getTheSocket() == null) {
+			createSocket();
 		}
-		return this.getTheSocket();
+		return getTheSocket();
 	}
 
 	private void createSocket() throws IOException {
@@ -174,7 +172,6 @@ public class MulticastSendingMessageHandler extends UnicastSendingMessageHandler
 
 	/**
 	 * If acknowledge = true; how many acks needed for success.
-	 *
 	 * @param minAcksForSuccess The minimum number of acks that will represent success.
 	 */
 	public void setMinAcksForSuccess(int minAcksForSuccess) {
@@ -183,7 +180,6 @@ public class MulticastSendingMessageHandler extends UnicastSendingMessageHandler
 
 	/**
 	 * Set the underlying {@link MulticastSocket} time to live property.
-	 *
 	 * @param timeToLive {@link MulticastSocket#setTimeToLive(int)}
 	 */
 	public void setTimeToLive(int timeToLive) {

spring-integration-ip/src/main/java/org/springframework/integration/ip/udp/UnicastSendingMessageHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2017 the original author or authors.
+ * Copyright 2001-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -83,8 +83,8 @@ public class UnicastSendingMessageHandler extends
 
 	private volatile int ackCounter = 1;
 
-	private volatile Map<String, CountDownLatch> ackControl = Collections
-			.synchronizedMap(new HashMap<String, CountDownLatch>());
+	private volatile Map<String, CountDownLatch> ackControl =
+			Collections.synchronizedMap(new HashMap<String, CountDownLatch>());
 
 	private volatile int soReceiveBufferSize = -1;
 
@@ -282,12 +282,7 @@ public class UnicastSendingMessageHandler extends
 			throw e;
 		}
 		catch (Exception e) {
-			try {
-				this.socket.close();
-			}
-			catch (Exception e1) {
-			}
-			this.socket = null;
+			closeSocketIfNeeded();
 			throw new MessageHandlingException(message, "failed to send UDP packet", e);
 		}
 		finally {
@@ -512,7 +507,7 @@ public class UnicastSendingMessageHandler extends
 		}
 		catch (IOException e) {
 			if (this.socket != null && !this.socket.isClosed()) {
-				logger.error("Error on UDP Acknowledge thread:" + e.getMessage());
+				logger.error("Error on UDP Acknowledge thread: " + e.getMessage());
 			}
 		}
 		finally {
@@ -530,7 +525,11 @@ public class UnicastSendingMessageHandler extends
 
 	private void closeSocketIfNeeded() {
 		if (this.socket != null) {
-			this.socket.close();
+			try {
+				this.socket.close();
+			}
+			catch (Exception e) {
+			}
 			this.socket = null;
 		}
 	}

spring-integration-ip/src/test/java/org/springframework/integration/ip/udp/UdpChannelAdapterTests.java

@@ -294,6 +294,7 @@ public class UdpChannelAdapterTests {
 		assertNotNull(receivedMessage);
 		assertEquals(new String(message.getPayload()), new String(receivedMessage.getPayload()));
 		adapter.stop();
+		handler.stop();
 	}
 
 	@Test
@@ -302,6 +303,8 @@ public class UdpChannelAdapterTests {
 		UnicastReceivingChannelAdapter adapter = new UnicastReceivingChannelAdapter(0);
 		adapter.setOutputChannel(channel);
 		ServiceActivatingHandler handler = new ServiceActivatingHandler(new FailingService());
+		handler.setBeanFactory(mock(BeanFactory.class));
+		handler.afterPropertiesSet();
 		channel.subscribe(handler);
 		QueueChannel errorChannel = new QueueChannel();
 		adapter.setErrorChannel(errorChannel);