Revert fix no exception thrown listening to an already registered host/port …

Author: hughbe

src/System.Net.HttpListener/src/System/Net/Managed/HttpEndPointManager.cs

@@ -102,18 +102,12 @@ private static void AddPrefixInternal(string p, HttpListener listener)
                 throw new HttpListenerException((int)HttpStatusCode.BadRequest, SR.net_invalid_path);
 
             // listens on all the interfaces if host name cannot be parsed by IPAddress.
-            HttpEndPointListener epl = GetEPListener(lp.Host, lp.Port, listener, lp.Secure, out bool alreadyExists);
-            if (alreadyExists)
-            {
-                throw new HttpListenerException(98, SR.Format(SR.net_listener_already, p));
-            }
+            HttpEndPointListener epl = GetEPListener(lp.Host, lp.Port, listener, lp.Secure);
             epl.AddPrefix(lp, listener);
         }
 
-        private static HttpEndPointListener GetEPListener(string host, int port, HttpListener listener, bool secure, out bool alreadyExists)
+        private static HttpEndPointListener GetEPListener(string host, int port, HttpListener listener, bool secure)
         {
-            alreadyExists = false;
-
             IPAddress addr;
             if (host == "*")
                 addr = IPAddress.Any;
@@ -146,7 +140,6 @@ private static HttpEndPointListener GetEPListener(string host, int port, HttpLis
             HttpEndPointListener epl = null;
             if (p.ContainsKey(port))
             {
-                alreadyExists = true;
                 epl = p[port];
             }
             else
@@ -208,7 +201,7 @@ private static void RemovePrefixInternal(string prefix, HttpListener listener)
             if (lp.Path.IndexOf("//", StringComparison.Ordinal) != -1)
                 return;
 
-            HttpEndPointListener epl = GetEPListener(lp.Host, lp.Port, listener, lp.Secure, out bool ignored);
+            HttpEndPointListener epl = GetEPListener(lp.Host, lp.Port, listener, lp.Secure);
             epl.RemovePrefix(lp, listener);
         }
     }