C＃UdpClient通过网络转发工作但不通过Internet转发

Question

好的，所以我一直在为我正在制作的程序开发服务器/客户端应用程序。它在本地网络上运行良好。我已设置端口转发，并使用我的外部IP地址与服务器应用程序进行通信。一切正常，但当我将客户端应用程序发送给我的朋友启动时，我的服务器没有与他们通信。有什么建议吗？

服务器（标出重要的行，其余部分不是解决此问题所必需的）

 class ServerListener
{
    private string _IPAddress;
    private int _Port;
    private static UdpState _UdpState;
    private static UdpClient _UdpServer;
    private IPEndPoint _IpEndpoint;
    private static BinaryFormatter _BinaryFormatter;

    public ServerListener(string ipAddress, int port)
    {
        _IPAddress = ipAddress;
        _Port = port;
        _UdpServer = new UdpClient(_Port);
        _IpEndpoint = new IPEndPoint(_IPAddress , 8000);
        _BinaryFormatter = new BinaryFormatter();
        ThreadPool.SetMaxThreads(50, 50);
        _UdpState = new UdpState();
        _UdpState.IpEndPoint = _IpEndpoint;
        _UdpState.UdpClient = _UdpServer;
        _UdpServer.Client.SendTimeout = 100;
        _UdpServer.Client.ReceiveTimeout = 100;
    }
    public void StartListenCycle()
    {
        FetchData();
    }

    private static void FetchData()
    {
        _UdpServer.BeginReceive(new AsyncCallback(ReceiveCallback), _UdpState);                  
    }

    private static void ReceiveCallback(IAsyncResult ar)
    {
        FetchData();
        ClientDataRequest dataRequest;
        UdpClient udpClient = (UdpClient)((UdpState)(ar.AsyncState)).UdpClient;
        IPEndPoint endpoint = (IPEndPoint)((UdpState)(ar.AsyncState)).IpEndPoint;

//// ---->    This lines important  Byte[] receiveBytes = udpClient.EndReceive(ar, ref endpoint);
        using (var memStream = new MemoryStream())
        {
            memStream.Write(receiveBytes, 0, receiveBytes.Length);
            memStream.Seek(0, SeekOrigin.Begin);
            dataRequest = (ClientDataRequest)_BinaryFormatter.Deserialize(memStream);
            ThreadPool.QueueUserWorkItem(new WaitCallback(ClientRequestHandler.HandleRequest), dataRequest);              
        }

        using (var memStream = new MemoryStream())
        {
            GameState gameState = new GameState(true);
            SerializedGameState dataPacket = new SerializedGameState();
            dataPacket.Players = new PlayerInformation[GameState.Players.Count];
            gameState.ClientPlayerObjects.CopyTo(dataPacket.Players, 0);
            Serializer.Serialize(memStream, dataPacket);
            byte[] responseAsBytes = memStream.ToArray();
            try
            {
   //// ----> This lines important   udpClient.Send(responseAsBytes, responseAsBytes.Length,   endpoint);
            }
            catch (Exception e)
            {
                Console.WriteLine("");
            }
        }
    }
}

客户（再次相同）

 class ClientNetworkConnection
    {
        private string _IPAddress;
        private int _Port;
        UdpClient _UdpClient;
        IPEndPoint _IpEndpoint;

        public ClientNetworkConnection(string ipAddress, int port)
        {
            _IPAddress = ipAddress;
            _Port = port;
            _UdpClient = new UdpClient();
            _UdpClient.Ttl = 10;
            _UdpClient.AllowNatTraversal(true);
            _IpEndpoint = new IPEndPoint(IPAddress.Parse(_IPAddress), _Port);
            _UdpClient.Client.SendTimeout = 100;
            _UdpClient.Client.ReceiveTimeout = 100;
            _UdpClient.Connect(_IpEndpoint);
        }

        public void FetchData()
        {
            while (Thread.CurrentThread.IsAlive)
            {
                ClientDataRequest request = new ClientDataRequest();
                request.PlayerID = DataStore.PlayerId;
                request.PlayerName = DataStore.PlayerName;
                request.PlayerClicked = DataStore.MouseDown;
                request.ClickPosition = new Point(DataStore.MousePositionX, DataStore.MousePositionY);
                SerializedGameState response = new SerializedGameState();
                byte[] objectAsBytes;
                BinaryFormatter bf = new BinaryFormatter();
                using (MemoryStream ms = new MemoryStream())
                {
                    bf.Serialize(ms, request);
                    objectAsBytes = ms.ToArray();
                }
 /////// -------> Important networky stuff     _UdpClient.Send(objectAsBytes, objectAsBytes.Length);

                try
                {
/////// -------> Important networky stuff         var data = _UdpClient.Receive(ref _IpEndpoint);
                    using (var memStream = new MemoryStream())
                    {
                        memStream.Write(data, 0, data.Length);
                        memStream.Seek(0, SeekOrigin.Begin);
                        response = Serializer.Deserialize<SerializedGameState>(memStream);
                        GameState.SetClientStaticVariables(response);
                    }
                }
                catch (SocketException e)
                {
                    //Handle Socket exception
                }
            }
        }
    }