[wcf-discovery] ExclusiveAddressUse won't work. AcceptChannel() should nreturn...

[wcf-discovery] ExclusiveAddressUse won't work. AcceptChannel() should nreturn null when it is being closed.

mcs/class/System.ServiceModel.Discovery/System.ServiceModel.Discovery.Udp/UdpChannelListener.cs

@@ -98,6 +98,8 @@ namespace System.ServiceModel.Discovery.Udp
 			if (!accept_wait_handle.WaitOne (timeout))
 				throw new TimeoutException ();
 			accept_wait_handle.Reset ();
+			if (State != CommunicationState.Opened)
+				return null; // happens during Close() or Abort().
 			channel = new UdpDuplexChannel (this);
 			channel.Closed += delegate {
 				accept_wait_handle.Set ();

mcs/class/System.ServiceModel.Discovery/System.ServiceModel.Discovery.Udp/UdpDuplexChannel.cs

@@ -252,7 +252,6 @@ if (result == null) throw new ArgumentNullException ("result");
 				if (isMulticast) {
 					multicast_address = ip;
 					client = new UdpClient (new IPEndPoint (IPAddress.Any, port));
-					client.ExclusiveAddressUse = false;
 					client.JoinMulticastGroup (ip, binding_element.TransportSettings.TimeToLive);
 				}
 				else