Question

Is it possible to identify an earlier UDP client without keeping the socket open? I want to link an integer ID to each unique client, but I don’t want to keep any additional threads open.

//Receive (Server)

private static Int32 port = 11000;
private static UdpClient udpClient = new UdpClient(port);

public static void receive_threaded()
{
    Thread t = new Thread(() =>
    {
        while (true)
        {
            IPEndPoint remoteIPEndPoint = new IPEndPoint(IPAddress.Any, port);
            byte[] content = udpClient.Receive(ref remoteIPEndPoint);

            if (content.Length > 0)
            {
                string message = Encoding.UTF8.GetString(content);
                if (action_message_receive != null) action_message_receive(String.Format("Recv({0}): {1}", remoteIPEndPoint.Port, message));
                parseMessage(message);
            }
        }
    });
    t.Start();
}

//Send (Client)

private static void send_message(string ip, string message)
{
    byte[] packetData = System.Text.UTF8Encoding.UTF8.GetBytes(message);

    int port = 11000;

    IPEndPoint ep = new IPEndPoint(IPAddress.Parse(ip), port);
    Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
    client.SendTo(packetData, ep);

    if (action_message_send != null) action_message_send("Send: " + message);
}

A client can request a (temporary) userID from the server, and the server will add it to it’s database and notify the client when it’s done doing that. However, I can’t have the client send it’s own userID when it’s making requests because any memory altering application would mean a ‘hacker’ could gain access to other user’s stuff.

Since the socket doesn’t stay open, the IPEndPoint.Port changes every time the client sends something to the server, so I can’t keep track of it with that. I could get it done by creating a username/pass on a userID request and having those sent on every single request involving the userID thereafter, but that would be silly.

So is there any way to do this without keeping a thread open for each client? I’m probably doing something really weird here because UDP is supposed to be a one way street, but I’m here to learn so I just had to ask.

Answer 1

You will need to introduce some sort of unique identifier chosen by the server and sent to the client for it to “behave and send it back for identification purposes”. A random long integer should suffice.

UDP has neither connections nor identification/authentication mechanisms. If you want those, use TCP (but those can be bruteforced also…)