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我需要确定向我发送多播数据包的机器的 IP，以便我可以通过单播对其进行响应。

我正在使用以下 csharp (.Net 3.5) 代码通过多播连接接收数据包（为简洁起见，对代码进行了编辑，删除了错误检查和不相关的选项）：

IPEndPoint LocalHostIPEnd = new IPEndPoint(IPAddress.Any, 8623);
Socket UDPSocket = new Socket(AddressFamily.InterNetwork,SocketType.Dgram,ProtocolType.Udp); 
UDPSocket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.MulticastLoopback, 1);

UDPSocket.Bind(LocalHostIPEnd);

//Join the multicast group
UDPSocket.SetSocketOption(
     SocketOptionLevel.IP,
     SocketOptionName.AddMembership,
     new MulticastOption(IPAddress.Parse("225.2.2.6")));

IPEndPoint LocalIPEndPoint = new IPEndPoint(IPAddress.Any ,Target_Port); 
EndPoint LocalEndPoint = (EndPoint)LocalIPEndPoint; 

// Create the state object. 
StateObject state = new StateObject();
state.buffer.Initialize();
state.workSocket = UDPSocket;
state.id = "state0";
//Set up my callback
UDPSocket.BeginReceiveMessageFrom(
    state.buffer, 
    0,
    StateObject.BufferSize, 
    0,
    ref LocalEndPoint, 
    new AsyncCallback(ReceiveCallback), 
    state);

这是回调，我正在尝试获取源 IP：

private void ReceiveCallback( IAsyncResult ar ) 
{
    IPEndPoint LocalIPEndPoint = new IPEndPoint(IPAddress.Any, Target_Port);
    EndPoint LocalEndPoint = (EndPoint)LocalIPEndPoint;

    // Read data from the remote device. 
    // The following code attempts to determine the IP of the sender,
    // but instead gets the IP of the multicast group.
    SocketFlags sFlags = new SocketFlags();
    IPPacketInformation ipInf = new IPPacketInformation();

    int bytesRead = client.EndReceiveMessageFrom(ar, ref sFlags,
        ref LocalEndPoint, out ipInf);

    log.Warn("Got address: " + ipInf.Address.ToString());
}

我知道正确的源 IP 在 IP 标头中，因为当我在 Wireshark 中嗅探数据包时，我可以清楚地看到它。但是，上面的代码并没有打印出发送系统的 IP (192.168.3.4)，而是打印出我订阅的多播组的 IP (225.2.2.6)。有没有办法获取源IP？

4

1 回答 1

3

Isn't your answer in the LocalEndPoint variable, which is the EndPoint of the packet's source, i.e., the dude on the other end. Note that I would probably rename this variable something like "remoteEP", and initialize it to something non-specific to avoid confusion.

于 2010-02-18T20:50:34.870 回答