Xamarin MulticastLock 获取不允许多播

Question

我正在使用 Xamarin 创建一个 Android 应用程序。此应用程序必须接收多播流。服务器发送正常，但我的应用程序接收不正确。如果我获得多播锁，这就是我的研究表明我需要做的所有事情，我可以看到我有锁，但应用程序仍然没有收到数据。

var wifiManager = var wifiManager = (WifiManager)Application.Context.GetSystemService(Context.WifiService);
// Acquire the lock
if (wifiManager != null)
{
    // _lock is a private member WifiManager.MulticastLock _lock
    _lock = wifiManager.CreateMulticastLock("PiEar");

    if (_lock != null)
    {
        _lock.Acquire();
    } 
    else
    {
        Debug.WriteLine("Could not acquire multicast lock"); // Does not print, meaning I do acquire the lock (and _lock.IsHeld() returns true)
    }
} 
else 
{
    Debug.WriteLine("WifiManager is null"); // Does not print, meaning it is not null
}

如果我随后使用不同的应用程序 MSniffer，它不仅会接收数据，而且还允许我的应用程序接收数据。我在尝试获取锁时做错了什么吗？

另外，我有以下权限：

ACCESS_WIFI_STATE
CHANGE_WIFI_STATE
ACCESS_NETWORK_STATE
互联网
CHANGE_WIFI_MULTICAST_STATE

编辑 1：更多信息

.cs 页面的相关代码如下。 _receivedMessages 是一个 ListView，让我可以直观地看到接收到的数据。上面的代码就是下面line 2上的运行。依赖服务中唯一的代码就是获取锁的代码。

var service = DependencyService.Get<IMulticastLock>();
service.Acquire();
Task.Run(async () =>
{
    while (true)
    {
        try
        {
            var endpoint = new IPEndPoint(IPAddress.Parse("224.0.0.69"), 6666);
            var multicast = new UdpClient(endpoint);
            while (true)
            {

                var multicastBytes = await multicast.ReceiveAsync();
                var message = Encoding.UTF8.GetString(multicastBytes.Buffer);
                Debug.WriteLine($"Received: {message}");
                Device.BeginInvokeOnMainThread(() =>
                {
                    _receivedMessages.Add(message);
                });
            }
        }
        catch (Exception e)
        {
            Debug.WriteLine(e);
        }
    }
});

Answer 1

检查 IP 地址和端口。

您可以尝试使用下面关于如何创建和配置 UdpClient 的代码。

public class MulticastUdpClient
{
 UdpClient _udpclient;
 int _port;
 IPAddress _multicastIPaddress;
 IPAddress _localIPaddress;
 IPEndPoint _localEndPoint;
 IPEndPoint _remoteEndPoint;

 public MulticastUdpClient(IPAddress multicastIPaddress, int port, IPAddress localIPaddress = null)
 {
     // Store params
     _multicastIPaddress = multicastIPaddress;
     _port = port;
     _localIPaddress = localIPaddress;
     if (localIPaddress == null)
         _localIPaddress = IPAddress.Any;

     // Create endpoints
     _remoteEndPoint = new IPEndPoint(_multicastIPaddress, port);
     _localEndPoint = new IPEndPoint(_localIPaddress, port);

     // Create and configure UdpClient
     _udpclient = new UdpClient();
     // The following three lines allow multiple clients on the same PC
     _udpclient.ExclusiveAddressUse = false;
     _udpclient.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
     _udpclient.ExclusiveAddressUse = false;
     // Bind, Join
     _udpclient.Client.Bind(_localEndPoint);
     _udpclient.JoinMulticastGroup(_multicastIPaddress, _localIPaddress);

     // Start listening for incoming data
     _udpclient.BeginReceive(new AsyncCallback(ReceivedCallback), null);
 }

 /// <summary>
 /// Send the buffer by UDP to multicast address
 /// </summary>
 /// <param name="bufferToSend"></param>
 public void SendMulticast(byte[] bufferToSend)
 {
     _udpclient.Send(bufferToSend, bufferToSend.Length, _remoteEndPoint);
 }

 /// <summary>
 /// Callback which is called when UDP packet is received
 /// </summary>
 /// <param name="ar"></param>
 private void ReceivedCallback(IAsyncResult ar)
 {
     // Get received data
     IPEndPoint sender = new IPEndPoint(0, 0);
     Byte[] receivedBytes = _udpclient.EndReceive(ar, ref sender);

     // fire event if defined
     if (UdpMessageReceived != null)
         UdpMessageReceived(this, new UdpMessageReceivedEventArgs() { Buffer = receivedBytes });

     // Restart listening for udp data packages
     _udpclient.BeginReceive(new AsyncCallback(ReceivedCallback), null);
 }

 /// <summary>
 /// Event handler which will be invoked when UDP message is received
 /// </summary>
 public event EventHandler<UdpMessageReceivedEventArgs> UdpMessageReceived;

 /// <summary>
 /// Arguments for UdpMessageReceived event handler
 /// </summary>
 public class UdpMessageReceivedEventArgs: EventArgs
 {
     public byte[] Buffer {get;set;}
 }

}

Xamarin MulticastLock 获取不允许多播

Xamarin MulticastLock Acquiring doesn't allow multicast

c#

xamarin

xamarin.forms

xamarin.android

multicast

编辑 1：更多信息