Проверка с помощью DTD — соединение принудительно закрыто

Я проверяю документ с DTD в документе, которого нет на моей машине, он хранится в Интернете.

В настоящее время я получаю следующее исключение

System.Xml.XmlException: An error has occurred while opening external DTD 'http://xml.cxml.org/schemas/cXML/1.2.020/cXML.dtd': Unable to connect to the remote server ---> 
System.Net.WebException: Unable to connect to the remote server --->
System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host 216.109.104.11:80
   
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   
at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)
   --- End of inner exception stack trace ---
   
at System.Net.HttpWebRequest.GetResponse()
   
at System.Xml.XmlDownloadManager.GetNonFileStream(Uri uri, ICredentials credentials)
   
at System.Xml.XmlDownloadManager.GetStream(Uri uri, ICredentials credentials)
  
at System.Xml.XmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn)
   
at System.Xml.XmlTextReaderImpl.OpenStream(Uri uri)
   
at System.Xml.XmlTextReaderImpl.DtdParserProxy_PushExternalSubset(String systemId, String publicId)
   --- End of inner exception stack trace ---
   
at System.Xml.XmlTextReaderImpl.Throw(Exception e)
   
at System.Xml.XmlTextReaderImpl.DtdParserProxy_PushExternalSubset(String systemId, String publicId)
   
at System.Xml.XmlTextReaderImpl.DtdParserProxy.System.Xml.IDtdParserAdapter.PushExternalSubset(String systemId, String publicId)
   
at System.Xml.DtdParser.ParseExternalSubset()
   
at System.Xml.DtdParser.ParseInDocumentDtd(Boolean saveInternalSubset)
   
at System.Xml.DtdParser.Parse(Boolean saveInternalSubset)
   
at System.Xml.XmlTextReaderImpl.ParseDoctypeDecl()
   
at System.Xml.XmlTextReaderImpl.ParseDocumentContent()
   
at System.Xml.XmlTextReaderImpl.Read()
   
at System.Xml.XmlValidatingReaderImpl.Read()
   
at System.Xml.XmlLoader.LoadDocSequence(XmlDocument parentDoc)
   
at System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace)
   
at System.Xml.XmlDocument.Load(XmlReader reader)
   
at cXML.ResponseFactory..ctor(HttpRequest request) :: System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host 216.109.104.11:80
   
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   
at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)
   --- End of inner exception stack trace ---
   
at System.Net.HttpWebRequest.GetResponse()
   
at System.Xml.XmlDownloadManager.GetNonFileStream(Uri uri, ICredentials credentials)
   
at System.Xml.XmlDownloadManager.GetStream(Uri uri, ICredentials credentials)
   at System.Xml.XmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn)
   
at System.Xml.XmlTextReaderImpl.OpenStream(Uri uri)
   
at System.Xml.XmlTextReaderImpl.DtdParserProxy_PushExternalSubset(String systemId, String publicId) :: System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host 216.109.104.11:80
   
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   
at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP)
   
at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)

Я знаю, что файл доступен, так как я могу перейти к нему. Но почему .NET не может получить к нему доступ?! Заранее спасибо.