对简单代理服务器进行故障排除

Question

我已经使用System.Net和System.Net.Sockets的同步方法和类用C#编写了一个简单的代理服务器。除了一个小故障之外，大多数事情都已经完成了。

当我从代理客户端(比如www.google.com)浏览url时，它可以很好地打开。当我做一个关键字搜索的时候，也没问题。但是，当我单击搜索结果时，客户端再次在屏幕上看到google.com主页！！但是，客户端浏览器url栏仍显示所单击的搜索结果url。也许这是因为google结果页面没有提供指向结果url的直接链接，而是指向google本身的链接，而我认为我代码中的中继逻辑无法处理这一点。你能帮我弄一下这个吗？我的代码如下：( ThreadHandleClient()方法是处理所有客户端请求并中继请求和响应的重要方法)

    public void Start(IPAddress ip, int port)
    {
        try
        {
            TcpListener listener = new TcpListener(ip, port);
            listener.Start(100);
            while (!stopFlag)
            {
                Socket client = listener.AcceptSocket();
                IPEndPoint rep = (IPEndPoint)client.RemoteEndPoint;
                Thread th = new Thread(ThreadHandleClient);
                th.Start(client);
            }

            listener.Stop();
        }
        catch (Exception ex)
        {
            Debug.Print("START: " + ex.Message);
        }
    }

    public void Stop()
    {
        stopFlag = true;    
    }

    public void ThreadHandleClient(object o)
    {
        try
        {
            Socket client = (Socket)o;
            Debug.Print("lingerstate=" + client.LingerState.Enabled.ToString() + " timeout=" + client.LingerState.LingerTime.ToString());
            NetworkStream ns = new NetworkStream(client);
            //RECEIVE CLIENT DATA
            byte[] buffer = new byte[2048];
            int rec = 0, sent = 0, transferred = 0, rport = 0;
            string data = "";
            do
            {
                rec = ns.Read(buffer, 0, buffer.Length);
                data += Encoding.ASCII.GetString(buffer, 0, rec);
            } while (rec == buffer.Length);

            //PARSE DESTINATION AND SEND REQUEST
            string line = data.Replace("\r\n", "\n").Split(new string[] { "\n" }, StringSplitOptions.None)[0];
            Uri uri = new Uri(line.Split(new string[] { " " }, StringSplitOptions.None)[1]);
            Debug.Print("CLIENT REQUEST RECEIVED: " + uri.OriginalString);
            if (uri.Scheme == "https")
            {
                rport = 443;
                Debug.Print("HTTPS - 443");

                //rq = HttpVersion + " 200 Connection established\r\nProxy-Agent: Prahlad`s Proxy Server\r\n\r\n";
                //ClientSocket.BeginSend(Encoding.ASCII.GetBytes(rq), 0, rq.Length, SocketFlags.None, new AsyncCallback(this.OnOkSent), ClientSocket);
            }
            else
            {
                rport = 80;
                Debug.Print("HTTP - 443");
            }
            IPHostEntry rh = Dns.GetHostEntry(uri.Host);
            Socket webserver = new Socket(rh.AddressList[0].AddressFamily, SocketType.Stream, ProtocolType.IP);
            webserver.Connect(new IPEndPoint(rh.AddressList[0], rport));
            byte[] databytes = Encoding.ASCII.GetBytes(data);
            webserver.Send(databytes, databytes.Length, SocketFlags.None);
            Debug.Print("SENT TO SERVER. WILL NOW RELAY: " + data);

            //START RELAY
            buffer = new byte[2048];
            bool firstTime = true;
            rec = 0;
            data = "";
            do
            {
                transferred = 0;
                do
                {
                    if (webserver.Poll((firstTime ? 9000 : 2000) * 1000, SelectMode.SelectRead))
                    {
                        rec = webserver.Receive(buffer, buffer.Length, SocketFlags.None);
                        Debug.Print("RECEIVED FROM WEBSERVER[" + rec.ToString() + "]: " + Encoding.ASCII.GetString(buffer, 0, rec));
                        firstTime = false;
                        sent = client.Send(buffer, rec, SocketFlags.None);
                        Debug.Print("SENT TO CLIENT[" + sent.ToString() + "]: " + Encoding.ASCII.GetString(buffer, 0, rec));
                        transferred += rec;
                    }
                    else
                    {
                        Debug.Print("No data polled from webserver");
                    }
                } while (rec == buffer.Length);

                Debug.Print("loop-1 finished");

                //if (transferred == 0)
                //     break;

                //transferred = 0;
                rec = 0;
                do
                {
                    if (client.Poll(1000 * 1000, SelectMode.SelectRead))
                    {
                        rec = client.Receive(buffer, buffer.Length, SocketFlags.None);
                        Debug.Print("RECEIVED FROM CLIENT: " + Encoding.ASCII.GetString(buffer, 0, rec));

                        sent = webserver.Send(buffer, rec, SocketFlags.None);
                        Debug.Print("SENT TO WEBSERVER[" + sent.ToString() + "]: " + Encoding.ASCII.GetString(buffer, 0, rec));
                        transferred += rec;
                    }
                    else
                    {
                        Debug.Print("No data polled from client");
                    }
                } while (rec == buffer.Length);
                Debug.Print("loop-2 finished");

            } while (transferred > 0);
            Debug.Print("LOOP ENDS. EXITING THREAD");
            client.Close();
            webserver.Close();
        }
        catch (Exception ex)
        {
            Debug.Print("Error occured: " + ex.Message);
        }
        finally {
            Debug.Print("Client thread closed");
        }
    }

Answer 1

经过反复试验，我找到了解决方案，因此我回答了我自己的问题。我的中继逻辑的问题是它用于双向中继，即从webserver->client和client->webserver进行中继。我意识到转发第二部分可能会在重定向中带来麻烦，因为在重定向中，报头的url部分("GET http://debian.org HTTP/1.1")会突然改变，因此它将不同于被中继的web服务器！！例如，谷歌重定向指向debian.org，而代理仍然会中继来自google.com而不是debian.org的流量。为了避免这种情况，我删除了第二个中继部分(即client->webserver)。如果一个客户端发送了一个新的请求，最好在一个单独的线程中处理，这样它就会被定向到正确的url主机。所以，我所要做的就是注释掉我的中继逻辑中的第二个内部循环：

                //rec = 0;
                //do
                //{
                //    if (client.Poll(3000 * 1000, SelectMode.SelectRead))
                //    {
                //        rec = client.Receive(buffer, buffer.Length, SocketFlags.None);
                //        Debug.Print("RECEIVED FROM CLIENT: " + Encoding.ASCII.GetString(buffer, 0, rec));

                //        sent = webserver.Send(buffer, rec, SocketFlags.None);
                //        Debug.Print("SENT TO WEBSERVER[" + sent.ToString() + "]: " + Encoding.ASCII.GetString(buffer, 0, rec));
                //        transferred += rec;
                //    }
                //    else
                //    {
                //        Debug.Print("No data polled from client");
                //    }
                //} while (rec == buffer.Length);
                //Debug.Print("loop-2 finished");