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I create a socket and bind it to a unicast address. However, it reads packets sent to the broadcast address and I do not understand why.

IPAddress ip;
IPAddress.TryParse("X.X.X.99", out ip);

Socket receiver = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
receiver.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
receiver.Bind(new IPEndPoint(ip, 9999));

byte rcvBuffer = new byte[1500];
int bytesRead = receiver.Receive(rcvBuffer);

With this code I receive packets addressed to both "x.x.x.255:9999" and "x.x.x.99:9999" and do not understand why. Anyone know why?
Updated 7-Jun-12 11:15am
Amund Gjersøe 8-Jun-12 14:54pm    
I started thinking about multicast when I saw the IP ending with 255. Reading about UDP multicast could clear things up. You could test my app Basic UDP Receiver to see if you get the same behavior using UdpClient, which is in the System.Net.Sockets-namespace.
Edit: Broadcast was it I was thinking about of course ;)
Joshi, Rushikesh 8-Jun-12 16:09pm    
I don't know it has anything with Subnet, if you have Subnet then change that value to

1 solution

This is broadcast, not multicast. the x.x.x.255 is a broadcast address.
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