Cross domain policy file over net.tcp for WCF servicehost and Silverlight 5 - wcf

Question

I have a locally hosted WCF service and a silverlight 5 app that communicates with it. By default silverlight tries to obtain the cross domain policy file over HTTP when making calls to the WCF service. I need to change this so that the policy file is served over net.tcp port 943 instead.
I have setup a local tcp listener that serves up the policy file over port 943 and i have followed this technique whereby i make a dummy socket connection in order to obtain the policy file over tcp as it is only retrieved once per application lifetime. The tcp server is being hit as expected and i am getting SocketError property value as Success (though i must note, the first time i hit the tcp server after starting the listener, the result is always access denied).
From what i can tell, the policy file is either invalid as the silverlight application as still unable to connect or the above mentioned technique does not work with silverlight 5.
What i would like to know is if what i am doing is possible & im doing it correctly, otherwise if there is an alternative means to have the policy file successfully downloaded over tcp and removing the need for retrieving it over HTTP.
Thanks

Answer 1

I wrote a long post about hosting silverlight in WPF - and using WCF with a http listener here:
How can I host a Silverlight 4 application in a WPF 4 application?
Now while not directly answering your question, it does show how to create a http version of the policy file.
I have also written something that serves up a policy listener over port 943, but I can't find where I posted the source - so I'll keep digging. As far as I remember though, silverlight does a cascade find of the policy file, if it doesn't get a connection on port 80, it'll then look on port 943.
I hope this is of some help somewhere.
Ok, here is the policy listener I had for net.TCP transport i.e. not HTTP based. I presume you have sorted this by now, sorry for the delay. It may well be of use to someone else now.
I was looking for the MS thing that said they cascade from HTTP to TCP, however, I can't, and therefore have to assume it was bunk and then changed.
Either way, if you call using a net.TCP service, and want a listener for it, this code should help:
#region "Policy Listener"
// This is a simple policy listener
// that provides the cross domain policy file for silverlight applications
// this provides them with a network access policy
public class SocketPolicyListener
{
private TcpListener listener = null;
private TcpClient Client = null;
byte[] Data;
private NetworkStream netStream = null;
private string listenaddress = "";
// This could be read from a file on the disk, but for now, this gives the silverlight application
// the ability to access any domain, and all the silverlight ports 4502-4534
string policyfile = "<?xml version='1.0' encoding='utf-8'?><access-policy><cross-domain-access><policy><allow-from><domain uri='*' /></allow-from><grant-to><socket-resource port='4502-4534' protocol='tcp' /></grant-to></policy></cross-domain-access></access-policy>";
// the request that we're expecting from the client
private string _policyRequestString = "<policy-file-request/>";
// Listen for our clients to connect
public void Listen(string ListenIPAddress)
{
listenaddress = ListenIPAddress;
if (listener == null)
{
listener = new TcpListener(IPAddress.Parse(ListenIPAddress), 943);
// Try and stop our clients from lingering, keeping the socket open:
LingerOption lo = new LingerOption(true, 1);
listener.Server.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Linger,lo);
}
listener.Start();
WaitForClientConnect();
}
private void WaitForClientConnect()
{
listener.BeginAcceptTcpClient(new AsyncCallback(OnClientConnected), listener);
}
public void StopPolicyListener()
{
if (Client.Connected)
{
// Should never reach this point, as clients
// are closed if they request the policy
// only clients that open the connection and
// do not submit a policy request will remain unclosed
Client.Close();
}
listener.Stop();
}
public void RestartPolicyListener()
{
listener.Start();
}
// When a client connects:
private void OnClientConnected(IAsyncResult ar)
{
if (ar.IsCompleted)
{
// Get the listener that handles the client request.
TcpListener listener = (TcpListener)ar.AsyncState;
// End the operation and display the received data on
// the console.
Client = listener.EndAcceptTcpClient(ar);
// Try and stop our clients from lingering, keeping the socket open:
LingerOption lo = new LingerOption(true, 1);
Client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Linger, lo);
// Set our receive callback
Data = new byte[1024];
netStream = Client.GetStream();
netStream.BeginRead(Data, 0, 1024, ReceiveMessage, null);
}
WaitForClientConnect();
}
// Read from clients.
public void ReceiveMessage(IAsyncResult ar)
{
int bufferLength;
try
{
bufferLength = Client.GetStream().EndRead(ar);
// Receive the message from client side.
string messageReceived = Encoding.ASCII.GetString(Data, 0, bufferLength);
if (messageReceived == _policyRequestString)
{
// Send our policy file, as it's been requested
SendMessage(policyfile);
// Have to close the connection or the
// silverlight client will wait around.
Client.Close();
}
else
{
// Continue reading from client.
Client.GetStream().BeginRead(Data, 0, Data.Length, ReceiveMessage, null);
}
}
catch (Exception ex)
{
throw new Exception(Client.Client.RemoteEndPoint.ToString() + " is disconnected.");
}
}
// Send the message.
public void SendMessage(string message)
{
try
{
byte[] bytesToSend = System.Text.Encoding.ASCII.GetBytes(message);
//Client.Client.Send(bytesToSend,SocketFlags.None);
Client.GetStream().Write(bytesToSend,0, bytesToSend.Length);
Client.GetStream().Flush();
}
catch (Exception ex)
{
throw ex;
}
}
}
#endregion