6933618: java/net/MulticastSocket/NoLoopbackPackets.java fails when rerun

Reviewed-by: alanb

test/java/net/MulticastSocket/NoLoopbackPackets.java

@@ -29,9 +29,7 @@
 import java.util.*;
 import java.net.*;
 
-
 public class NoLoopbackPackets {
-    private static int PORT = 9001;
     private static String osname;
 
     static boolean isWindows() {
@@ -68,13 +66,19 @@ public class NoLoopbackPackets {
             return;
         }
 
+        MulticastSocket msock = null;
+        List<SocketAddress> failedGroups = new ArrayList<SocketAddress>();
+        try {
+            msock = new MulticastSocket();
+            int port = msock.getLocalPort();
+
             // we will send packets to three multicast groups :-
             // 224.1.1.1, ::ffff:224.1.1.2, and ff02::1:1
             //
             List<SocketAddress> groups = new ArrayList<SocketAddress>();
-        groups.add(new InetSocketAddress(InetAddress.getByName("224.1.1.1"), PORT));
-        groups.add(new InetSocketAddress(InetAddress.getByName("::ffff:224.1.1.2"), PORT));
-        groups.add(new InetSocketAddress(InetAddress.getByName("ff02::1:1"), PORT));
+            groups.add(new InetSocketAddress(InetAddress.getByName("224.1.1.1"), port));
+            groups.add(new InetSocketAddress(InetAddress.getByName("::ffff:224.1.1.2"), port));
+            groups.add(new InetSocketAddress(InetAddress.getByName("ff02::1:1"), port));
 
             Thread sender = new Thread(new Sender(groups));
             sender.setDaemon(true); // we want sender to stop when main thread exits
@@ -83,12 +87,10 @@ public class NoLoopbackPackets {
             // Now try to receive multicast packets. we should not see any of them
             // since we disable loopback mode.
             //
-        MulticastSocket msock = new MulticastSocket(PORT);
             msock.setSoTimeout(5000);       // 5 seconds
 
             byte[] buf = new byte[1024];
             DatagramPacket packet = new DatagramPacket(buf, 0, buf.length);
-        List<SocketAddress> failedGroups = new ArrayList<SocketAddress>();
             for (SocketAddress group : groups) {
                 msock.joinGroup(group, null);
 
@@ -103,6 +105,9 @@ public class NoLoopbackPackets {
 
                 msock.leaveGroup(group, null);
             }
+        } finally {
+            if (msock != null) try { msock.close(); } catch (Exception e) {}
+        }
 
         if (failedGroups.size() > 0) {
             System.out.println("We should not receive anything from following groups, but we did:");
@@ -111,9 +116,8 @@ public class NoLoopbackPackets {
             throw new RuntimeException("test failed.");
         }
     }
-}
 
-class Sender implements Runnable {
+    static class Sender implements Runnable {
         private List<SocketAddress> sendToGroups;
 
         public Sender(List<SocketAddress> groups) {
@@ -137,10 +141,11 @@ class Sender implements Runnable {
                         msock.send(packet);
                     }
 
-                Thread.currentThread().sleep(1000);     // 1 second
+                    Thread.sleep(1000);     // 1 second
                 }
             } catch (Exception e) {
                 throw new RuntimeException(e);
             }
         }
+    }
 }