最近的Silverlight開發(fā)中，由于部分需求對實時性和數(shù)據(jù)量下載速度有要求，部分WCF服務(wù)配置成了netTcpBinding，這種方式跟普通的service.svc寄宿IIS不同的是，Silverlight需要的策略文件需要放置在本機(jī)IIS的根下，也就是wwwroot文件夾下，以滿足Silverlight在以TCP協(xié)議調(diào)用本機(jī)WCF服務(wù)時請求策略文件。
（注：Silverlight通過TCP協(xié)議調(diào)用WCF服務(wù)時，會以http方式請求主機(jī)的一個策略文件，地址是http://localhost/clientaccesspolicy.xml)
這其實是個不太好的選擇，程序運(yùn)行的所需的環(huán)境被分成了兩部分，同事的機(jī)器上并未安裝IIS，為了大家開發(fā)簡便，不用在額外安裝IIS，也為了讓程序更加獨立，我就想能不能寫代碼監(jiān)控80端口模擬IIS向Silverlight輸出這個策略文件。
解決方法
有了這個想法之后，首先想到的是通過Socket進(jìn)行監(jiān)聽，因為此前在MSDN上看到過這種方式，但很無奈，將代碼轉(zhuǎn)移過來之后，并未成功。相信做過Silverlight在Socket方面應(yīng)用的朋友對下面這個PolicyServer類很熟悉吧。
using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
namespace PolicyServer
{
// Encapsulate and manage state for a single connection from a client
class PolicyConnection
{
private Socket m_connection;
// buffer to receive the request from the client
private byte[] m_buffer;
private int m_received;
// the policy to return to the client
private byte[] m_policy;
// the request that we're expecting from the client
private static string s_policyRequestString = "<policy-file-request/>";
public PolicyConnection(Socket client, byte[] policy)
{
m_connection = client;
m_policy = policy;
m_buffer = new byte[s_policyRequestString.Length];
m_received = 0;
try
{
// receive the request from the client
m_connection.BeginReceive(m_buffer, 0, s_policyRequestString.Length, SocketFlags.None, new AsyncCallback(OnReceive), null);
}
catch (SocketException)
{
m_connection.Close();
}
}
// Called when we receive data from the client
private void OnReceive(IAsyncResult res)
{
try
{
m_received += m_connection.EndReceive(res);
// if we haven't gotten enough for a full request yet, receive again
if (m_received < s_policyRequestString.Length)
{
m_connection.BeginReceive(m_buffer, m_received, s_policyRequestString.Length - m_received, SocketFlags.None, new AsyncCallback(OnReceive), null);
return;
}
// make sure the request is valid
string request = System.Text.Encoding.UTF8.GetString(m_buffer, 0, m_received);
if (StringComparer.InvariantCultureIgnoreCase.Compare(request, s_policyRequestString) != 0)
{
m_connection.Close();
return;
}
// send the policy
m_connection.BeginSend(m_policy, 0, m_policy.Length, SocketFlags.None, new AsyncCallback(OnSend), null);
}
catch (SocketException)
{
m_connection.Close();
}
}
// called after sending the policy to the client; close the connection.
public void OnSend(IAsyncResult res)
{
try
{
m_connection.EndSend(res);
}
finally
{
m_connection.Close();
}
}
}
// Listens for connections on port 943 and dispatches requests to a PolicyConnection
class PolicyServer
{
private Socket m_listener;
private byte[] m_policy;
// pass in the path of an XML file containing the socket policy
public PolicyServer(string policyFile)
{
// Load the policy file
FileStream policyStream = new FileStream(policyFile, FileMode.Open);
m_policy = new byte[policyStream.Length];
policyStream.Read(m_policy, 0, m_policy.Length);
policyStream.Close();
m_listener = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
m_listener.SetSocketOption(SocketOptionLevel.IPv6, (SocketOptionName)27, 0);
m_listener.Bind(new IPEndPoint(IPAddress.IPv6Any, 943));
m_listener.Listen(10);
m_listener.BeginAccept(new AsyncCallback(OnConnection), null);
}
public void OnConnection(IAsyncResult res)
{
Socket client = null;
try
{
client = m_listener.EndAccept(res);
}
catch (SocketException)
{
return;
}
// handle this policy request with a PolicyConnection
PolicyConnection pc = new PolicyConnection(client, m_policy);
// look for more connections
m_listener.BeginAccept(new AsyncCallback(OnConnection), null);
}
public void Close()
{
m_listener.Close();
}
}
public class Program
{
static void Main(string[] args)
{
if (args.Length == 0)
{
Console.WriteLine("usage: PolicyServer.exe PolicyFile.xml");
return;
}
PolicyServer ps = new PolicyServer(args[0]);
System.Threading.Thread.Sleep(System.Threading.Timeout.Infinite);
}
}
}
此路不通之后，又想起使用HttpListener類，看看是否能夠監(jiān)聽http請求，果然能夠截獲HTTP的請求 HttpListener listener = new HttpListener(); listener.Prefixes.Add(http://localhost/); listener.Start();Console.WriteLine("開始監(jiān)聽…"); HttpListenerContext context = listener.GetContext(); HttpListenerRequest request = context.Request; HttpListenerResponse response = context.Response; 但是這種方式有個明顯的缺點，就是線程是阻塞的。于是，又想到使用線程池。 System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(Listen)); private static void Listen(object state) { while (httpListener.IsListening) { httpListener.BeginGetContext(new AsyncCallback(ListenerCallback), httpListener); listenForNextRequest.WaitOne(); } }
這樣的話，每接收一個請求便會異步處理這個請求。在請求的處理上，接收請求后需要向外輸出策略文件流，供silverlight端接收驗證。
using(System.Net.HttpListenerResponse response = context.Response)
{ System.Threading.Thread.Sleep(1000); string responseString = "<?xml version=\"1.0\" encoding=\"utf-8\"?> " + " <access-policy> " + " <cross-domain-access> " + " <policy> " + " <allow-from http-request-headers=\"*\">" + " <domain uri=\"*\" /> " + " </allow-from> " + " <grant-to> " + " <socket-resource port=\"4502-4534\" protocol=\"tcp\" /> " + " </grant-to> " + " </policy> " + " </cross-domain-access>" + " </access-policy>"; byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString); response.ContentLength64 = buffer.LongLength; response.OutputStream.Write(buffer, 0, buffer.Length); }
啟動這個模擬服務(wù)，將clientaccesspolicy從wwwroot中移除后再運(yùn)行一下程序，OK，我們不再需要將策略文件放到IIS下了。
注意：如果你的機(jī)器裝了IIS，請還是放一個策略文件到wwwroot吧，否則就停掉IIS再使用這個類，因為IIS和這個類只能有一方監(jiān)聽80端口。
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