/**Proxy.cs：C# Programming Tips & Techniquesby Charles Wright, Kris JamsaPublisher: Osborne/McGraw-Hill (December 28, 2001)ISBN: 0072193794*/// Proxy.cs -- Implements a multi-threaded Web proxy server////    Compile this program with the following command line://     C:>csc Proxy.csusing System;using System.Net;using System.Net.Sockets;using System.Text;using System.IO;using System.Threading;namespace nsProxyServer{ public class ProxyServer {  static public void Main (string [] args)  {   int Port = 3125;   if (args.Length > 0)   {    try    {     Port = Convert.ToInt32 (args[0]);    }    catch    {     Console.WriteLine ("Please enter a port number.");     return;    }   }   try   {    // Create a listener for the proxy port    TcpListener sockServer = new TcpListener (Port);    sockServer.Start ();    while (true)    {     // Accept connections on the proxy port.     Socket socket = sockServer.AcceptSocket ();     // When AcceptSocket returns, it means there is a connection. Create     // an instance of the proxy server class and start a thread running.     clsProxyConnection proxy = new clsProxyConnection (socket);     Thread thrd = new Thread (new ThreadStart (proxy.Run));     thrd.Start ();     // While the thread is running, the main program thread will loop around     // and listen for the next connection request.    }   }   catch (IOException e)   {    Console.WriteLine (e.Message);   }  } } class clsProxyConnection {  public clsProxyConnection (Socket sockClient)  {   m_sockClient = sockClient;  }  Socket m_sockClient; //, m_sockServer;  Byte [] readBuf = new Byte [1024];  Byte [] buffer = null;  Encoding ASCII = Encoding.ASCII;  public void Run ()  {   string strFromClient = "";   try   {    // Read the incoming text on the socket/    int bytes = ReadMessage (m_sockClient,           readBuf, ref strFromClient);    // If it's empty, it's an error, so just return.    // This will termiate the thread.    if (bytes == 0)     return;    // Get the URL for the connection. The client browser sends a GET command    // followed by a space, then the URL, then and identifer for the HTTP version.    // Extract the URL as the string betweeen the spaces.    int index1 = strFromClient.IndexOf (' ');    int index2 = strFromClient.IndexOf (' ', index1 + 1);    string strClientConnection =      strFromClient.Substring (index1 + 1, index2 - index1);    if ((index1 < 0) || (index2 < 0))    {     throw (new IOException ());    }    // Write a messsage that we are connecting.    Console.WriteLine ("Connecting to Site " +         strClientConnection);    Console.WriteLine ("Connection from " +         m_sockClient.RemoteEndPoint);    // Create a WebRequest object.    WebRequest req = (WebRequest) WebRequest.Create              (strClientConnection);    // Get the response from the Web site.    WebResponse response = req.GetResponse ();    int BytesRead = 0;    Byte [] Buffer = new Byte[32];    int BytesSent = 0;    // Create a response stream object.    Stream ResponseStream = response.GetResponseStream();    // Read the response into a buffer.    BytesRead = ResponseStream.Read(Buffer,0,32);    StringBuilder strResponse = new StringBuilder("");    while (BytesRead != 0)    {     // Pass the response back to the client     strResponse.Append(Encoding.ASCII.GetString(Buffer,          0, BytesRead));     m_sockClient.Send(Buffer, BytesRead, 0);     BytesSent += BytesRead;     // Read the next part of the response     BytesRead = ResponseStream.Read(Buffer, 0, 32);    }   }   catch (FileNotFoundException e)   {    SendErrorPage (404, "File Not Found", e.Message);   }   catch (IOException e)   {    SendErrorPage (503, "Service not available", e.Message);   }   catch (Exception e)   {     SendErrorPage (404, "File Not Found", e.Message);     Console.WriteLine (e.StackTrace);     Console.WriteLine (e.Message);   }   finally   {    // Disconnect and close the socket.    if (m_sockClient != null)    {     if (m_sockClient.Connected)     {      m_sockClient.Close ();     }    }   }   // Returning from this method will terminate the thread.  }  // Write an error response to the client.  void SendErrorPage (int status, string strReason, string strText)  {   SendMessage (m_sockClient, "HTTP/1.0" + " " +       status + " " + strReason + "/r/n");   SendMessage (m_sockClient, "Content-Type: text/plain" + "/r/n");   SendMessage (m_sockClient, "Proxy-Connection: close" + "/r/n");   SendMessage (m_sockClient, "/r/n");   SendMessage (m_sockClient, status + " " + strReason);   SendMessage (m_sockClient, strText);  }  // Send a string to a socket.  void SendMessage (Socket sock, string strMessage)  {   buffer = new Byte [strMessage.Length + 1];   int len = ASCII.GetBytes (strMessage.ToCharArray(),          0, strMessage.Length, buffer, 0);   sock.Send (buffer, len, 0);  }  // Read a string from a socket.  int ReadMessage (Socket sock, byte [] buf, ref string strMessage)  {   int iBytes = sock.Receive (buf, 1024, 0);   strMessage = Encoding.ASCII.GetString (buf);   return (iBytes);  } }}