remove unused code

client/src/main/java/org/apache/rocketmq/client/impl/factory/MQClientInstance.java

@@ -17,7 +17,6 @@
 package org.apache.rocketmq.client.impl.factory;
 
 import java.io.UnsupportedEncodingException;
-import java.net.DatagramSocket;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -118,7 +117,6 @@ public class MQClientInstance {
     private final ConsumerStatsManager consumerStatsManager;
     private final AtomicLong sendHeartbeatTimesTotal = new AtomicLong(0);
     private ServiceState serviceState = ServiceState.CREATE_JUST;
-    private DatagramSocket datagramSocket;
     private Random random = new Random();
 
     public MQClientInstance(ClientConfig clientConfig, int instanceIndex, String clientId) {
@@ -854,10 +852,6 @@ public class MQClientInstance {
                     this.mQClientAPIImpl.shutdown();
                     this.rebalanceService.shutdown();
 
-                    if (this.datagramSocket != null) {
-                        this.datagramSocket.close();
-                        this.datagramSocket = null;
-                    }
                     MQClientManager.getInstance().removeClientFactory(this.clientId);
                     log.info("the client factory [{}] shutdown OK", this.clientId);
                     break;