如何在C＃中确定组播数据包的源IP？

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响应它。

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，已编辑代码，并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IP头中有正确的源IP，因为当我在wireshark中嗅探数据包时，我可以清楚地看到它。 但是，上述代码不打印出发送系统的IP（192.168.3.4），而是打印出我订阅的组播组的IP（225.2.2.6）。 有没有办法获得源IP？

Answer 1

不是你在LocalEndPoint变量中的答案，它是数据包源的EndPoint，即另一端的dude。 请注意，我可能会将此变量重命名为“remoteEP”，并将其初始化为非特定的变量以避免混淆。