asynchronous sockets

The following code should do the trick. I am on a guest machine so I have not had a chance to compile or run this code, but the following code snippet should give you the general idea:

class StateObject { public byte[] buffer; public Socket sock; } public void ReceiveBroadcastMessages() { IPAddress mcastAddress; int mcastPort; Socket mcastSocket; MulticastOption mcastOption; mcastAddress = IPAddress.Parse("15.15.15.15"); mcastPort = 56000; byte[] bytes = new byte[1024]; IPEndPoint groupEP = new IPEndPoint(mcastAddress, mcastPort); EndPoint remoteEP = (EndPoint) new IPEndPoint(IPAddress.Any,0); string temp = ""; int i = 0; try { mcastSocket = new Socket(AddressFamily.InterNetwork,SocketType.Dgram,ProtocolType.Udp); IPAddress localIPAddr = IPAddress.Parse("20.20.20.20"); EndPoint localEP = (EndPoint)new IPEndPoint(localIPAddr, mcastPort); mcastSocket.Bind(localEP); mcastOption = new MulticastOption(mcastAddress, localIPAddr); mcastSocket.SetSocketOption(SocketOptionLevel.IP,SocketOptionName.AddMembership,mcastOption); StateObject so = new StateObject(); so.buffer = bytes; so.sock = mcastSocket; // this call will not block mcastSocket.BeginReceiveFrom(bytes, 0, bytes.Length, SocketFlags.Multicast, ref remoteEP, new AsyncCallback(MyCallback), so); //i = mcastSocket.ReceiveFrom(bytes,ref remoteEP); //Blocking code temp = groupEP.ToString() + System.Text.Encoding.ASCII.GetString(bytes,0,bytes.Length); mcastSocket.Close(); } catch (Exception e) { string a = e.Message ; } } public void MyCallback(IAsyncResult ar) { StateObject so = (StateObject)ar.AsyncState; Socket mcastSocket = so.sock; IPEndPoint ipPoint = new IPEndPoint(IPAddress.Any, 0); EndPoint remoteEP = (EndPoint) ipPoint; int read = EndReceiveFrom(ar, ref remoteEP); // remoteEP should now contain who sent the datagram if (read > 0){ // consume the bytes in so.buffer (variable read holds how many bytes there are of data in the buffer) // post another receive mcastSocket.BeginReceiveFrom(so.buffer,0,so.buffer.Length,SocketFlags.Multicast,so); } else { // no data was read } }

MikeFlasko at 2007-9-9 >

mahjayar wrote:

One small correction, this line // this call will not block mcastSocket.ReceiveFrom(bytes, 0, bytes.Length, SocketFlags.Multicast, ref remoteEP, new AsyncCallback(MyCallback), so); should be // this call will not block mcastSocket.BeginReceiveFrom(bytes, 0, bytes.Length, SocketFlags.Multicast, ref remoteEP, new AsyncCallback(MyCallback), so);

this line crashes with errorcode 10045, but with SocketFlags.None its fine

//exception thrown

_socket.BeginReceiveFrom( _receiveBuffer, 0, _receiveBuffer.Length, SocketFlags.Multicast, ref _ep, _asyncReceive, null );

//no exception thrown

Valdair at 2007-9-9 >