C#从UDP消息中获取发件人地址 [英] C# Getting sender address from UDP message

问题描述

我有一个嵌入式以太网接口(Lantronix XPort)，它以其标识信息响应UDP广播.

I have an embedded Ethernet interface (Lantronix XPort) that responds to a UDP broadcast with its identifying information.

我能够多播魔术包"，并且侦听器可以正确接收数据报，但是我还需要找出发送该响应数据报的IP地址.如果是TCP，我会做socket.RemoteEndPoint，但是在应用于UDP套接字时会抛出异常.

I am able to multicast the "magic packet" and datagrams are received by the listener correctly, however I also need to find out what IP Address send that response datagram. If it were TCP, I would do socket.RemoteEndPoint, but that throws an exception when applied to a UDP socket.

public class Program
{
    public static void Main(string[] args)
    {
        // magic packet
        byte[] magicPacket = new byte[4] { 0, 0, 0, 0xf6 };

        // set up listener for response
        Socket sendSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

        // EDIT: Also, had to add this to for it to broadcast correctly
        sendSocket.EnableBroadcast = true;
        IPEndPoint listen_ep = new IPEndPoint(IPAddress.Any, 0);
        sendSocket.Bind(listen_ep);

        // set up broadcast message
        EndPoint send_ep = new IPEndPoint(IPAddress.Parse("192.168.255.255"), 30718);
        sendSocket.SendTo(magicPacket, magicPacket.Length, SocketFlags.None, send_ep);

        DateTime dtStart = DateTime.Now;
        while (true)
        {
            if (sendSocket.Available > 0)
            {
                byte[] data = new byte[2048];
                // throws SocketException
                //IPEndPoint ip = sendSocket.RemoteEndPoint as IPEndPoint;
                sendSocket.Receive(data, SocketFlags.None);
                if (data.Length > 4)
                {
                    PrintDevice(data);
                }
            }

            if (DateTime.Now > dtStart.AddSeconds(5))
            {
                break;
            }

            Console.WriteLine(".");

            Thread.Sleep(100);
        }

        // wait for keypress to quit
        Console.WriteLine("Press any key to exit.");
        Console.ReadKey();
    }
} 

有什么想法吗?是否有更好的策略来读取响应数据报，以便让我确定远程IP地址?

Any thoughts? Is there a better strategy to reading the response datagrams that would let me ascertain the Remote IP Address?

通常，我在SO上发表的那一刻，清晰的一刻击中了我.

As is typical, the minute I post on SO, a moment of clarity hits me.

结果证明我可以这样做:

Turns out I can just do this:

                EndPoint remote_ep = new IPEndPoint(IPAddress.Any, 0);
                // Use ReceiveFrom instead of Receieve
                //sendSocket.Receive(data, SocketFlags.None);
                sendSocket.ReceiveFrom(data, ref remote_ep);

remote_ep现在包含远程端点信息！

And remote_ep now contains the remote endpoint information!

推荐答案

看看

Take a look at ReceiveFrom instead of Receive, it will let you pass in a reference to an Endpoint.

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