why is the UDPclient multicast not working?

Question

public void send_multicast(string message)
    {
        UdpClient c = new UdpClient(10102);
        Byte[] sendBytes = Encoding.ASCII.GetBytes(message); 
        IPAddress m_GrpAddr = IPAddress.Parse("224.0.0.1");
        IPEndPoint ep = new IPEndPoint(m_GrpAddr,10102);   
        c.MulticastLoopback=true;
         c.JoinMulticastGroup(m_GrpAddr);
        c.Send(sendBytes,sendBytes.Length,ep);
        Console.WriteLine(message);
    }

    public string recv_multicast()
    {
        Console.WriteLine("was here");
        String strData = "";
        //String Ret = "";
        ASCIIEncoding ASCII = new ASCIIEncoding();
        UdpClient c = new UdpClient(10101);

        // Establish the communication endpoint.
        IPEndPoint endpoint = new IPEndPoint(IPAddress.Any, 10101);
         IPAddress m_GrpAddr = IPAddress.Parse("224.0.0.1");

         c.JoinMulticastGroup(m_GrpAddr);
            Byte[] data = c.Receive(ref endpoint);
            strData = ASCII.GetString(data);
            //Ret += strData + "\n";

        return strData;
    }

is there anything wrong with the ports?

the recv method is getting blocked but is not receiving the message?

In wireshark I can see the message going from local addr port 10102 to 224.0.0.1 dest_port 0, but the recv is not getting the msg from the multicast addr.

BTW I am running both instances on the same computer. reference : http://msdn.microsoft.com/en-us/library/ekd1t784.aspx

**Got the solution:In send routine

IPEndPoint ep = new IPEndPoint(m_GrpAddr,10102);

should be

IPEndPoint ep = new IPEndPoint(m_GrpAddr,10101);

the port of receiving**

Polynomial · Accepted Answer · 2011-10-20T08:18:41.830

1

You need to enable multicast loopback in order to recieve packets sent by yourself.

http://msdn.microsoft.com/en-us/library/system.net.sockets.udpclient.multicastloopback.aspx

You should use JoinMulticastGroup on the server side as well as the client side. If that fails, you can also try using Wireshark (google it) to see if the packets are actually sent.

edited Oct 20 '11 at 08:18

answered Oct 20 '11 at 08:08

Polynomial

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I set i to true in send_multicast, but no effect – Oct 20 '11 at 08:10
Please edit your question to reflect the changes you made to the code. – Polynomial Oct 20 '11 at 08:12
It may be that your router doesn't support IGMP. Without it, multicast won't work. – Polynomial Oct 20 '11 at 08:37
thanks, but due to your wireshark idea I got the solution, it was with the ports. – Oct 20 '11 at 09:18
2

If you could add a section to the end of your original question detailing your working code and the fix, that'd be great. Might give someone else the answer in future :) – Polynomial Oct 20 '11 at 10:05

why is the UDPclient multicast not working?

1 Answers1