为什么订阅了多播组的UDP套接字正在接收非多播消息?

在客户端,我执行以下操作:

1. 设置监听套接字以订阅和接收服务器发起的多播消息。
2. 设置一个接收套接字,以接收服务器对客户端多播的响应
   

一切正常,除了两个接收套接字最终都会收到服务器对客户端的(非多播)响应。我不清楚这是否是预期的行为。我可以把两个接收插座减少到一个吗?#1订阅了服务器的多播,#2只是在同一端口上监听来自服务器的直接传输(来自服务器的非多播消息)。我可以安全地移除第二个接收插座吗?

客户代码:

// 1. Set up a socket and asynchronously listen for server startup multicasts.
Socket listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
    ProtocolType.Udp);
listenSocket.SetSocketOption(SocketOptionLevel.Socket,
    SocketOptionName.ReuseAddress, 1);
listenSocket.Bind(new IPEndPoint(IPAddress.Any, 50000));
listenSocket.SetSocketOption(SocketOptionLevel.IP,SocketOptionName.AddMembership,
    new MulticastOption(IPAddress.Parse("239.1.1.1")));
EndPoint clientEndPoint = new IPEndPoint(0, 0);
listenSocket.BeginReceiveFrom(receiveBuffer, 0, receiveBuffer.Length,
    SocketFlags.None, ref clientEndPoint,
    new AsyncCallback(OnServerMessageReceived), (object)this);

// 2. Set up socket to receive the server's response to client's multicast.
Socket receiveSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
    ProtocolType.Udp);
receiveSocket.SetSocketOption(SocketOptionLevel.Socket,
    SocketOptionName.ReuseAddress, 1);
receiveSocket.Bind(new IPEndPoint(IPAddress.Any, 50000));
receiveSocket.ReceiveTimeout = 3000; // Timeout after 3 seconds.

// 3. Send a multicast message for server to respond to.
Socket sendSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
    ProtocolType.Udp);
EndPoint multicastEndPoint = new IPEndPoint(IPAddress.Parse("239.1.1.2"), 50000);
sendSocket.SendTo(packet, packet.Length, SocketFlags.None, multicastEndPoint);

// 4. Wait for server to respond to the multicast message (timeout = 3 seconds).
byte[] receiveBuff = new byte[2048];
EndPoint serverEndPoint = new IPEndPoint(0, 0);
int bytesRead = receiveSocket.ReceiveFrom(receiveBuff, ref serverEndPoint);

// Receive multicast message sent from client (in asynchronous callback method).
EndPoint clientEndPoint = new IPEndPoint(0, 0);
int bytesRead = listenSocket.EndReceiveFrom(asyncResult, ref clientEndPoint);

// Send response back to the client (change port to 50000).
EndPoint destination = new IPEndPoint((clientEndPoint as IPEndPoint).Address,
    50000);
Socket responseSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
    ProtocolType.Udp);
responseSocket.SendTo(response, response.Length, SocketFlags.None, destination);