Get the IpAddress on which we received an UDP Multicast request

Question

I'm using an UdpClient to read data from a multicast group.

It's configured like this:

m_udpClientReceiver = new UdpClient();
m_receivingEndPoint = new IPEndPoint(IPAddress.Any, m_port);
m_udpClientReceiver.ExclusiveAddressUse = false;
m_udpClientReceiver.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
m_udpClientReceiver.ExclusiveAddressUse = false;
m_udpClientReceiver.Client.Bind(m_receivingEndPoint);
m_udpClientReceiver.JoinMulticastGroup(m_multicastAddress, 255);

and I read it with:

Byte[] data = m_udpClientReceiver.Receive(ref m_receivingEndPoint);

I've several network cards(two LAN, one wifi), that are bound on differents subnets. I need to know on which network card(which ip in fact) the request has been received.

How can I achieve this?

Thank you!

Answer 1

I'm finally using the BeginReceive method(async), and I'm giving as context the ip on which it's bound

Answer 2

As an alternative have you considered not joining a multicast group? You can send and receive multicast packets just as easily using the standard UDPClient class. i.e.

UdpClient.Send(byte[] dgram, int bytes, IPEndPoint endPoint)

where endPoint = new IPEndPoint(IPAddress.Broadcast, <port number>). And on the receive still using:

Byte[] data = m_udpClientReceiver.Receive(ref m_receivingEndPoint);

where m_receivingEndPoint is now correctly set? I've just tested this and it works fine.