[HttpListener] Match exceptions from MS on cleanup.

	When the listener is aborted or closed, we get different exceptions
	depending on whether there's a GetContext() call in progress or not.

mcs/class/System/System.Net/HttpListener.cs

@@ -177,8 +177,9 @@ void Cleanup (bool close_existing)
 				}
 
 				lock (wait_queue) {
+					Exception exc = new ObjectDisposedException ("listener");
 					foreach (ListenerAsyncResult ares in wait_queue) {
-						ares.Complete ("Listener was closed.");
+						ares.Complete (exc);
 					}
 					wait_queue.Clear ();
 				}
@@ -218,6 +219,9 @@ public HttpListenerContext EndGetContext (IAsyncResult asyncResult)
 			ListenerAsyncResult ares = asyncResult as ListenerAsyncResult;
 			if (ares == null)
 				throw new ArgumentException ("Wrong IAsyncResult.", "asyncResult");
+			if (ares.EndCalled)
+				throw new ArgumentException ("Cannot reuse this IAsyncResult");
+			ares.EndCalled = true;
 
 			if (!ares.IsCompleted)
 				ares.AsyncWaitHandle.WaitOne ();
@@ -247,7 +251,8 @@ public HttpListenerContext GetContext ()
 			if (prefixes.Count == 0)
 				throw new InvalidOperationException ("Please, call AddPrefix before using this method.");
 
-			IAsyncResult ares = BeginGetContext (null, null);
+			ListenerAsyncResult ares = (ListenerAsyncResult) BeginGetContext (null, null);
+			ares.InGet = true;
 			return EndGetContext (ares);
 		}
 

mcs/class/System/System.Net/ListenerAsyncResult.cs

@@ -42,21 +42,24 @@ class ListenerAsyncResult : IAsyncResult {
 		HttpListenerContext context;
 		object locker = new object ();
 		ListenerAsyncResult forward;
+		internal bool EndCalled;
+		internal bool InGet;
 
 		public ListenerAsyncResult (AsyncCallback cb, object state)
 		{
 			this.cb = cb;
 			this.state = state;
 		}
 
-		internal void Complete (string error)
+		internal void Complete (Exception exc)
 		{
 			if (forward != null) {
-				forward.Complete (error);
+				forward.Complete (exc);
 				return;
 			}
-			//FIXME: error_code?
-			exception = new HttpListenerException (0, error);
+			exception = exc;
+			if (InGet && (exc is ObjectDisposedException))
+				exception = new HttpListenerException (500, "Listener closed");
 			lock (locker) {
 				completed = true;
 				if (handle != null)
@@ -109,7 +112,7 @@ internal void Complete (HttpListenerContext context, bool synch)
 					ListenerAsyncResult next = forward;
 					for (int i = 0; next.forward != null; i++) {
 						if (i > 20)
-							Complete ("Too many authentication errors");
+							Complete (new HttpListenerException (400, "Too many authentication errors"));
 						next = next.forward;
 					}
 				} else {

mcs/class/System/Test/System.Net/HttpListenerTest.cs

@@ -280,7 +280,6 @@ public void PropertiesWhenClosed3 ()
 		}
 
 		[Test]
-		[Category ("NotWorking")]  // we throw a HttpListenerException
 		public void CloseWhileBegin ()
 		{
 			HttpListener listener = new HttpListener ();
@@ -297,7 +296,6 @@ public void CloseWhileBegin ()
 		}
 
 		[Test]
-		[Category ("NotWorking")]  // we throw a HttpListenerException
 		public void AbortWhileBegin ()
 		{
 			HttpListener listener = new HttpListener ();