C# UdpClient cannot receive any messages

Question

Here are some critical codes. The DefaultPort is 53.

    public DNServer(int port = DefaultPort, int ttl = DefaultTTL, int cacheSize = DefaultCacheSize)
    {

        dnsCache = new Dictionary<string, DNSSet>();
        this.ttl = ttl;
        this.cacheSize = cacheSize;

        udpListener = new UdpClient(port);

    }

    public void Start()
    {
        while (true)
        {
            IPEndPoint clientEndPoint = new IPEndPoint(IPAddress.Any,53);
            byte[] requestBytes = udpListener.Receive(ref clientEndPoint);

            DNSRequest request = DNSRequest.Parse(requestBytes);
            DNSResponse response = ProcessRequest(request);

            byte[] responseBytes = response.GetBytes();
            udpListener.Send(responseBytes, responseBytes.Length, clientEndPoint);

           
        }
    }

I am trying to simulate a local DNS server with C#. When I started the application, flushed the DNS cache and visited a new webpage, it just got stuck in udpListener.Receive(). Wireshark can detect the DNS request successfully.

The port has been opened. After I started the application, use 'netstat -ano' and it shows the port 53 is active.

 UDP    0.0.0.0:53             *:*                                    27660

The expected result should be that when I am opening a new page in my browser, the application can detect the DNS request sent by my computer.