Using udpclient with multiple network adapters

Question

3.00/5 (1 vote)

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I'm using UdpClient which works fine with a single adapter, but on a machine with hyper-v installed (multiple virtual adapters) the code does not get a response.

Has anyone encountered this and a workaround?

What I have tried:

C#

private string DoUDPSearch(int port)
{
    var host = Dns.GetHostEntry(Dns.GetHostName());
    string ipaddr = "";
    foreach (var ip in host.AddressList)
    {
        if (ip.AddressFamily == AddressFamily.InterNetwork)
        {
            try
            {
                var Client = new UdpClient();
                Client.Client.SendTimeout = 2000;
                Client.Client.ReceiveTimeout = 2000;
                var RequestData = Encoding.ASCII.GetBytes("SomeRequestData");
                var ServerEp = new IPEndPoint(ip, 0);

                Client.EnableBroadcast = true;
                Client.Send(RequestData, RequestData.Length, new IPEndPoint(IPAddress.Broadcast, port));

                var ServerResponseData = Client.Receive(ref ServerEp);
                var ServerResponse = Encoding.ASCII.GetString(ServerResponseData);
                //Console.WriteLine("Recieved {0} from {1}", ServerResponse, ServerEp.Address.ToString());
                ipaddr = ServerEp.Address.ToString();
                logger("Server IP = " + ServerEp.Address);
                Client.Close();

                return ipaddr;
            }
            catch { Console.WriteLine("unable to connect."); }
        }
    }
    logger("Server IP not found.");
    return ipaddr;
}

Posted 10-Dec-16 5:17am

Mehdi Gholam

Updated 10-Dec-16 21:43pm

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Comments

Afzaal Ahmad Zeeshan 10-Dec-16 13:09pm

UDP protocol itself doesn't guarantee any response or delivery. That is the job of TCP. Does TCP work fine in this case as I have not worked in virtualized adapter system?

I worked with "TCP or UDP case" 2 years ago, and left using it in favor of TCP. UDP tends to be fast, so it keeps dropping everything.

Anyways, have a look at this thread.

Richard MacCutchan 11-Dec-16 3:22am

Are you sure that you have network paths between all the nodes? Did the remote devices receive the broadcast messages?

Mehdi Gholam 11-Dec-16 3:44am

Found the problem with a lot of tinkering... (wee hee!!), see solution 2

2 solutions

Solution 1

Try to increase your hosts OS UDP Buffer Size:

For Win:

C#

[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet\Services\Afd\Parameters]

DefaultReceiveWindow = 10240
DefaultSendWindow = 10240

Please comment if that didn't helped.

Posted 10-Dec-16 11:12am

El_Codero

Comments

Mehdi Gholam 11-Dec-16 0:55am

Didn't help.

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Mehdi Gholam · Accepted Answer · 2016-12-10T21:43:00

Found the problem, the client should send with port = 0 [ServerEp] and it will receive a response on the correct port of the server (if you set the client port send to be = the server's port [ServerEp] it will always work regardless which is not what you want).

The correct code is below:

C#

private string DoUDPSearch(int port)
{
    var host = Dns.GetHostEntry(Dns.GetHostName());
    string ipaddr = "";
    foreach (var ip in host.AddressList)
    {
        if (ip.AddressFamily == AddressFamily.InterNetwork)
        {
            try
            {
                var ServerEp = new IPEndPoint(ip, 0);
                var Client = new UdpClient(ServerEp);
                Client.Client.SendTimeout = 2000;
                Client.Client.ReceiveTimeout = 2000;
                var RequestData = Encoding.ASCII.GetBytes("SomeRequestData");

                Client.Send(RequestData, RequestData.Length, new IPEndPoint(IPAddress.Broadcast, port));

                var ServerResponseData = Client.Receive(ref ServerEp);
                var ServerResponse = Encoding.ASCII.GetString(ServerResponseData);
                ipaddr = ServerEp.Address.ToString();
                logger("Server IP = " + ServerEp.Address);
                Client.Close();

                return ipaddr;
            }
            catch { Console.WriteLine("unable to connect."); }
        }
    }
    logger("Server IP not found.");
    return ipaddr;
}