粗糙的C#版HTTP代理

By;云舒

前些时候一个无锡人在我博客留言，说我读再多的书，也改变不了我是个程序员的本质。或许它觉得它是在鄙视我，不过我到觉得它是在赞扬我——我真的算不上是个程序员，写代码的能力实在是太烂了——不过我会努力的。

说说这段代码的问题吧。首先是字符串切割的问题，要将客户端提交过来的GET，POST等原始请求切割，分离出主机名，端口，URL等数据。这里用正则匹配是最好的，遗憾的是我不擅长此道，所以使用了手动切割的办法，很笨重繁琐，但是毕竟它工作得很好。第二个问题是Keep-Alive的问题，这里我没有处理好。最开始我在http proxy里面修改客户端请求，强行将keep-alive修改为close，但是发现在某些站点的时候会出错。于是使用了类似select的方法读取数据，直到超时关闭两端的连接。我猜测，这里如果解析content-length会更好，但是略微繁琐了点，还是等我仔细阅读下RFC再看怎么修改吧。第三个是CONNECT方法的问题，这个到很简单，转发数据就行了，因此是这个代码中写得最好的一部分，用来登陆QQ还是不错的。

说实话，我不喜欢HTTP这种太宽松的协议，感觉灵活得让我难以把握。直接看代码吧，我加了很多debug信息，真的要用就去掉好了。调用这个类很简单，看main函数的实现就好了。为了方便贴代码，我写的时候就把三个类写到一个文件里面去了。顺便要说的是，虽然有类，但是没有任何面向对象的东西——这也再次证明，其实我算不上一个程序员，最多是个代码爱好者。

using System;

using System.Net;

using System.Net.Sockets;

using System.Text;

using System.IO;

using System.Threading;

using System.Collections;

namespace HttpProxy

{

public class HttpProxy

{

int ProxyPort;

/// <summary>

/// 代理服务器入口类构造函数

/// </summary>

/// <param name="Port">Http Proxy监听的端口</param>

public HttpProxy( int Port)

{

ProxyPort = Port;

}

/// <summary>

/// 启动Http代理服务器

/// </summary>

public void Start( )

{

TcpListener tcplistener = null;

try

{

// 开始监听端口

tcplistener = new TcpListener(Dns.GetHostAddresses(Dns.GetHostName())[0], ProxyPort);

tcplistener.Start();

Console.WriteLine("侦听端口号: " + ProxyPort.ToString());

}

catch (Exception e)

{

Console.WriteLine("启动代理服务器失败: " + e.Message);

}

while (true)

{

try

{

// 接受客户端连接

Socket socket = tcplistener.AcceptSocket();

HttpSession Session = new HttpSession(socket);

// 启动新线程，处理连接

Thread thread = new Thread(new ThreadStart(Session.Start));

thread.Start();

}

catch( Exception e )

{

Console.WriteLine("接受客户端连接异常: " + e.Message );

}

}

}

}

public class HttpSession

{

// 客户端socket

Socket ClientSocket;

// 设定编码

Encoding ASCII = Encoding.ASCII;

/// <summary>

/// 构造函数

/// </summary>

/// <param name="socket">客户端socket</param>

public HttpSession(Socket socket)

{

this.ClientSocket = socket;

}

public void Start()

{

// 客户端缓冲区，读取客户端命令

Byte[] ReadBuff = new byte[1024 * 10];

try

{

int Length = ClientSocket.Receive(ReadBuff);

// 没有读到数据

if (0 == Length)

{

Console.WriteLine("从客户端读取命令错误");

ClientSocket.Shutdown(SocketShutdown.Both);

ClientSocket.Close();

return;

}

}

// 读取出现异常

catch (Exception e)

{

Console.WriteLine("读取客户端异常: " + e.Message);

}

// 来自客户端的HTTP请求字符串

string ClientMsg = ASCII.GetString(ReadBuff);

// 根据rnrn截取请求行

string Line = ClientMsg.Substring(0, ClientMsg.IndexOf("rn"));

string[] CmdArray = Line.Split(' ');

// GET http://www.test.com:80/index.php HTTP/1

// CONNECT www.test.com:443 HTTP/1

string Cmd = CmdArray[0];

string RawUrl = CmdArray[1];

Console.WriteLine("原始请求: ", Line);

// CONNECT请求

if (Cmd == "CONNECT")

{

DoConnect(RawUrl);

}

// GET,POST和其他

else

{

DoOther(RawUrl, ClientMsg);

}

}

/// <summary>

/// 处理CONNECT命令，此处作用是支持QQ，MSN，以及多级代理串联等

/// </summary>

/// <param name="RawUrl"></param>

private void DoConnect( string RawUrl )

{

string[] Args = RawUrl.Split( ':' );

string Host = Args[0];

int Port = int.Parse(Args[1]);

Socket ServerSocket = null;

try

{

IPAddress[] IpList = Dns.GetHostEntry(Host).AddressList;

Console.WriteLine("尝试连接:", IpList[0], Port);

ServerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

ServerSocket.Connect(IpList[0], Port);

}

catch (Exception e)

{

Console.WriteLine("连接真实服务器异常: " + e.Message);

}

// 连接真实服务器成功

if (ServerSocket.Connected)

{

ClientSocket.Send( ASCII.GetBytes("HTTP/0 200 Connection establishedrnrn") );

}

else

{

ClientSocket.Shutdown(SocketShutdown.Both);

ClientSocket.Close();

}

// 开始转发数据

ForwardTcpData(ClientSocket, ServerSocket);

}

/// <summary>

/// 处理GET，POST等命令。使用了POLL，在代理服务器中强制去掉了Keep-Alive能力

/// </summary>

/// <param name="RawUrl"></param>

/// <param name="ClientMsg"></param>

public void DoOther(string RawUrl, string ClientMsg)

{

RawUrl = RawUrl.Substring(0 + "http://".Length);

int Port;

string Host;

string Url;

// 下面是分割处理请求，此处应该用正则匹配，不过我不擅长，因此手动切割，—_—!

int index1 = RawUrl.IndexOf(':');

// 没有端口

if (index1 == -1)

{

Port = 80;

int index2 = RawUrl.IndexOf('/');

// 没有目录

if (index2 == -1)

{

Host = RawUrl;

Url = "/";

}

else

{

Host = RawUrl.Substring(0, index2);

Url = RawUrl.Substring(index2);

}

}

else

{

int index2 = RawUrl.IndexOf('/');

// 没有目录

if (index2 == -1)

{

Host = RawUrl.Substring(0, index1);

Port = IntParse(RawUrl.Substring(index1 + 1));

Url = "/";

}

else

{

// /出现在:之前，则说明:后面的不是端口

if (index2 < index1)

{

Host = RawUrl.Substring(0, index2);

Port = 80;

}

else

{

Host = RawUrl.Substring(0, index1);

Port = IntParse(RawUrl.Substring(index1 + 1, index2 - index1 - 1));

}

Url = RawUrl.Substring(index2);

}

}

Console.WriteLine("Host is:, Port is:, Url is:", Host, Port, Url);

IPAddress[] address = null;

try

{

IPHostEntry IPHost = Dns.GetHostEntry(Host);

address = IPHost.AddressList;

Console.WriteLine("Web服务器IP地址: " + address[0]);

}

catch( Exception e )

{

Console.WriteLine( "解析服务器地址异常: " + e.Message );

}

Socket IPsocket = null;

try

{

// 连接到真实WEB服务器

IPEndPoint ipEndpoint = new IPEndPoint(address[0], Port);

IPsocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

IPsocket.Connect(ipEndpoint);

// 对WEB服务器端传送HTTP请求命令，将原始HTTP请求中HTTP PROXY部分包装去掉

string ReqData = ClientMsg;

// 改写头中的URL,从http://www.test.com/index.php改为/index.php

ReqData = ReqData.Replace("http://"+RawUrl, Url);

// 按照rn切分HTTP头

string[] ReqArray = ReqData.Split(new string[1]{"rn"}, StringSplitOptions.None);

ReqData = "";

// 改写Keep-Alive等字段

for (int index = 0; index < ReqArray.Length; index++)

{

/*

if (ReqArray[index].StartsWith("Accept-Encoding:"))

{

ReqArray[index] = "Accept-Encoding: deflate";

}

*/

if (ReqArray[index].StartsWith("Proxy-Connection:"))

{

ReqArray[index] = ReqArray[index].Replace("Proxy-Connection:", "Connection:");

//ReqArray[index] = "Connection: close";

}

/*

else if (ReqArray[index].StartsWith("Keep-Alive:"))

{

ReqArray[index] = "";

}

*/

// 修改后的字段组合成请求

if( ReqArray[index] != "" )

{

ReqData = ReqData + ReqArray[index] + "rn";

}

}

ReqData = ReqData.Trim();

byte[] SendBuff = ASCII.GetBytes(ReqData);

IPsocket.Send(SendBuff);

}

catch( Exception e )

{

Console.WriteLine( "发送请求到服务器异常: " + e.Message );

}

// 使用Poll来判断完成，某些站点会出问题

while (true)

{

Byte[] RecvBuff = new byte[1024 * 20];

try

{

if( !IPsocket.Poll( 15 * 1000 * 1000, SelectMode.SelectRead ) )

{

Console.WriteLine("HTTP超时，关闭连接");

break;

}

}

catch (Exception e)

{

Console.WriteLine("Poll: " + e.Message);

break;

}

int Length = 0;

try

{

Length = IPsocket.Receive(RecvBuff);

if (0 == Length)

{

Console.WriteLine("服务端关闭");

break;

}

Console.WriteLine("从服务端收到字节", Length);

}

catch (Exception e)

{

Console.WriteLine("Recv: " + e.Message);

break;

}

try

{

Length = ClientSocket.Send(RecvBuff, Length, 0);

Console.WriteLine("发送字节到客户端", Length);

}

catch (Exception e)

{

Console.WriteLine("Send: " + e.Message);

}

}

/*

// 根据接收字节数来判断完成，某些站点会出问题

try

{

while (true)

{

Byte[] RecvBuff = new byte[1024 * 10];

int Length = IPsocket.Receive(RecvBuff);

if (Length <= 0)

{

Console.WriteLine("从服务端接收数据完成");

break;

}

Console.WriteLine("从服务端收到字节", Length);

Length = ClientSocket.Send(RecvBuff, Length, 0);

Console.WriteLine("发送字节到客户端", Length);

}

}

catch (Exception e)

{

Console.WriteLine(e.Message);

}

*/

try

{

ClientSocket.Shutdown(SocketShutdown.Both);

ClientSocket.Close();

IPsocket.Shutdown(SocketShutdown.Both);

IPsocket.Close();

}

catch (Exception e)

{

//Console.WriteLine(e.Message);

}

}

/// <summary>

/// 在客户端和服务器之间中转数据

/// </summary>

/// <param name="client">客户端socket</param>

/// <param name="server">服务端socket</param>

private void ForwardTcpData(Socket client, Socket server)

{

ArrayList ReadList = new ArrayList(2);

while (true)

{

ReadList.Clear();

ReadList.Add(client);

ReadList.Add(server);

try

{

Socket.Select(ReadList, null, null, 1 * 1000 * 1000);

}

catch (SocketException e)

{

Console.WriteLine("Select error: " + e.Message);

break;

}

// 超时

if (ReadList.Count == 0)

{

//Console.WriteLine("Time out");

continue;

}

// 客户端可读

if (ReadList.Contains(client))

{

byte[] Recv = new byte[1024 * 10];

int Length = 0;

try

{

Length = client.Receive(Recv, Recv.Length, 0);

if (Length == 0)

{

Console.WriteLine("Client is disconnect.");

break;

}

Console.WriteLine(" Recv bytes from client", Length);

}

catch (Exception e)

{

Console.WriteLine("Read from client error: " + e.Message);

break;

}

try

{

Length = server.Send(Recv, Length, 0);

Console.WriteLine(" Write bytes to server", Length);

}

catch (Exception e)

{

Console.WriteLine("Write data to server error: " + e.Message);

break;

}

}

// 真实服务端可读

if (ReadList.Contains(server))

{

byte[] Recv = new byte[1024 * 10];

int Length = 0;

try

{

Length = server.Receive(Recv, Recv.Length, 0);

if (Length == 0)

{

Console.WriteLine("Server is disconnect");

break;

}

Console.WriteLine("Recv bytes from server", Length);

}

catch (Exception e)

{

Console.WriteLine("Read from server error: " + e.Message);

break;

}

try

{

Length = client.Send(Recv, Length, 0);

Console.WriteLine(" Write bytes to client", Length);

}

catch (Exception e)

{

Console.WriteLine("Write data to client error: " + e.Message);

break;

}

}

}

try

{

client.Shutdown(SocketShutdown.Both);

server.Shutdown(SocketShutdown.Both);

client.Close();

server.Close();

}

catch (Exception e)

{

Console.WriteLine(e.Message);

}

finally

{

Console.WriteLine("转发完毕");

}

}

}

public class MainClass

{

public static void Main()

{

const int Port = 8080;

HttpProxy Proxy = new HttpProxy(Port);

Proxy.Start();

}

}

}