Fixed issue: NETTY-180 Channel.getRemoteAddress() can return null for a received MessageEvent when ExecutionHandler is in the pipeline.

* DatagramChannel implementations cache localAddresses now
* DatagramChannel implementations don't cache remoteAddress because a user can disconnect and then connect again.  However, MessageEvent.getRemoteAddress() will always have correct remoteAddress value, so it shouldn't be a problem at all.

src/main/java/org/jboss/netty/channel/socket/nio/NioDatagramChannel.java

@@ -120,6 +120,8 @@ class NioDatagramChannel extends AbstractChannel
      */
     volatile boolean inWriteNowLoop;
 
+    private volatile InetSocketAddress localAddress;
+
     NioDatagramChannel(final ChannelFactory factory,
             final ChannelPipeline pipeline, final ChannelSink sink,
             final NioDatagramWorker worker) {
@@ -142,13 +144,18 @@ class NioDatagramChannel extends AbstractChannel
     }
 
     public InetSocketAddress getLocalAddress() {
+        InetSocketAddress localAddress = this.localAddress;
+        if (localAddress == null) {
             try {
-            return (InetSocketAddress) datagramChannel.socket().getLocalSocketAddress();
+                this.localAddress = localAddress =
+                    (InetSocketAddress) datagramChannel.socket().getLocalSocketAddress();
             } catch (Throwable t) {
                 // Sometimes fails on a closed socket in Windows.
                 return null;
             }
         }
+        return localAddress;
+    }
 
     public InetSocketAddress getRemoteAddress() {
         try {

src/main/java/org/jboss/netty/channel/socket/oio/OioDatagramChannel.java

@@ -57,6 +57,7 @@ final class OioDatagramChannel extends AbstractChannel
     final Object interestOpsLock = new Object();
     private final DatagramChannelConfig config;
     volatile Thread workerThread;
+    private volatile InetSocketAddress localAddress;
 
     OioDatagramChannel(
             ChannelFactory factory,
@@ -87,11 +88,26 @@ final class OioDatagramChannel extends AbstractChannel
     }
 
     public InetSocketAddress getLocalAddress() {
-        return (InetSocketAddress) socket.getLocalSocketAddress();
+        InetSocketAddress localAddress = this.localAddress;
+        if (localAddress == null) {
+            try {
+                this.localAddress = localAddress =
+                    (InetSocketAddress) socket.getLocalSocketAddress();
+            } catch (Throwable t) {
+                // Sometimes fails on a closed socket in Windows.
+                return null;
+            }
+        }
+        return localAddress;
     }
 
     public InetSocketAddress getRemoteAddress() {
+        try {
             return (InetSocketAddress) socket.getRemoteSocketAddress();
+        } catch (Throwable t) {
+            // Sometimes fails on a closed socket in Windows.
+            return null;
+        }
     }
 
     public boolean isBound() {