C# Getting sender address from UDP message

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

I am able to multicast the "magic packet" and datagrams 开发者_JAVA技巧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();
    }
} 

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

EDIT:

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

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);

And remote_ep now contains the remote endpoint information!

---

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

---

What about Asynchronous socket?I didn't find any way to get the remote IP address. (Asynchronous method ReceiveFromAsync is my only option in wp8)

---

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

i think it works for IP but it fails for port number if you would notice

try chaging 0 to something else like 6530 4expl

it system will would generate it's random port number

Any ideas to why is it ?

P.S. Any ideas how can i change my user name here .... ?

FOUND IT : the abstract class only needed for representation of port it is in value not out

since there's no bind done before hand this operation ref EndPoint needed to represent the sender. Meaning that it is there to show senders port and IP not to specify from where to get the communication. And EndPoint instantiation is really just a formality seems like it is overriden by system with senders address anyway. I think it has to do somethign with the way UDP protocol works. But all in all the ref EndPoint is there only shows where u got the packet from and only it does not specify where u want u'r commuicatino to be from.