HDFS-13730. BlockReaderRemote.sendReadResult throws NPE. Contributed by Yuanbo Liu.

(cherry picked from commit 62ad9885ea8c75c134de43a3a925c76b253658e1)
(cherry picked from commit 45543ffd6af723bb83bd44a99f12165363c70abb)
(cherry picked from commit fc8983a5b8c94746d3e58cc203974aa09c1b640b)
(cherry picked from commit 79f8e4d5bc3afaff2f352b918e96a6ef3c2abcce)
(cherry picked from commit ce49f8a5df8b63c9bb2e50b4ad25a6bffd9e54de)

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/net/BasicInetPeer.java

@@ -21,6 +21,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.Socket;
+import java.net.SocketAddress;
 import java.nio.channels.ReadableByteChannel;
 
 import org.apache.hadoop.net.unix.DomainSocket;
@@ -93,7 +94,8 @@ public class BasicInetPeer implements Peer {
 
   @Override
   public String getRemoteAddressString() {
-    return socket.getRemoteSocketAddress().toString();
+    SocketAddress address = socket.getRemoteSocketAddress();
+    return address == null ? null : address.toString();
   }
 
   @Override

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/net/NioInetPeer.java

@@ -21,6 +21,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.Socket;
+import java.net.SocketAddress;
 import java.nio.channels.ReadableByteChannel;
 
 import org.apache.hadoop.net.SocketInputStream;
@@ -96,7 +97,8 @@ public class NioInetPeer implements Peer {
 
   @Override
   public String getRemoteAddressString() {
-    return socket.getRemoteSocketAddress().toString();
+    SocketAddress address = socket.getRemoteSocketAddress();
+    return address == null ? null : address.toString();
   }
 
   @Override