/**
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa

Publisher: 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.cs
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.IO;
using System.Threading;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;

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;
private static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
{
return true; //总是接受
}
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.
ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);

HttpWebRequest req = (HttpWebRequest)WebRequest.Create
(strClientConnection);
req.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 3.0.04506; .NET CLR 3.5.21019)";
// req.Headers.Add("UserAgent", "Mozilla/5.0 (Windows NT 6.1; rv:40.0) Gecko/20100101 Firefox/40.0");

// 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);
try
{
sock.Send(buffer, len, 0);
}
catch (Exception e) {
Console.WriteLine(e.Message);
}
}

// 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);
}
}
}