确定UDP主机是否可达

我有一个metro应用程序使用UDP通过wifi与设备交谈。但是，当我断开设备与网络的连接或在设备断开连接的情况下启动应用程序时，什么也没有发生。ConnectAsync不会抛出异常，应用也不会抛出异常，应用运行起来就像没什么问题一样。我不能ping到另一端但如果我给它一个格式化的字符串它会响应。该设备目前连接到一个可以上网的路由器，但我最终计划使用一个不能上网的路由器。我从来没有用UDP做过任何事情，所以我在这里不知所措。

这是一个UDP侦听器/写入器的实现(取自Pete Bright at 10rem.net)

class Network
    {
        private DatagramSocket _socket;
        public bool IsConnected { get; set; }
        public bool recieved;
        public string ret;

        public Network()
        {
            IsConnected = false;
            _socket = new DatagramSocket();
            _socket.MessageReceived += OnSocketMessageReceived;
        }
        public async void Connect(HostName remoteHostName, string remoteServiceNameOrPort)
        {
            try
            {
              await  _socket.ConnectAsync(remoteHostName, remoteServiceNameOrPort);
            }
            catch (Exception e)
            {
                    var msg = new MessageDialog(e.ToString());
                    msg.ShowAsync();
            }
            IsConnected = true;
        }

        private void OnSocketMessageReceived(DatagramSocket sender, DatagramSocketMessageReceivedEventArgs args)
        {
              var reader = args.GetDataReader();
                var count = reader.UnconsumedBufferLength;
                var data = reader.ReadString(count);
                ret = data.Trim();
                recieved = true;
        }

        DataWriter _writer =null;
        public async void SendMessage(string message)
        {
            if (String.IsNullOrEmpty(message)) return;
            if (_writer == null)
            {
                var stream = _socket.OutputStream;
                _writer = new DataWriter(stream);
            }
            _writer.WriteString(message);
            await _writer.StoreAsync();
        }            
    }