杨冶军

　　本人在用Oicq聊天时，经常收到一些好友发给我的用文本符号描绘的图像，觉得好羡慕啊，于是一想何
    我们一般常用的Internet代理服务器是用微软的Proxy Server 2.0 。但我们可以自己动手编写一个简
单、小型的Proxy Server 。下面介绍具体的实现方法。

一． 原理
本程序的结构原理如下：
对于每一个用户的请求（Internet 请求，由浏览器发出），本程序将启动两个线程，一个把本地用户的请求
数据发送到远程的Internet主机，另一个线程把远程主机的回应数据发送到本地请求用户。

二． 主要函数
    UserToProxyThread ( void * pParam ) ：它是用来把本地用户请求数据发送到远程主机的，起服务器线
程角色。当接到本地（局域网）用户的请求，它就启动另一个自身线程，以侦听别的用户的请求，并读出已接
收到的请求数据，接着启动第二个线程ProxyToServer()（这个线程用来连接远程主机），当远程主机连接成
功后，它把已读出的本地用户请求数据发送到远程主机。
    ProxyToServer ( void * pParam) ，可以被当作是客户端服务，它把远程主机发送来的数据分发给本地请
求用户。

三． 开发运行环境
    本程序是在VC++6.0环境下开发的，在Win95 和 WinNT4.0下运行正常。

四． 详细代码
#include "stdafx.h"
#include "Proxy.h"
#include < winsock2.h > //WINSOCKET API 2。0
#include < stdlib.h >
#include < stdio.h >
#include < string.h >
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
////////////////////////////////////////////////////////////////

#define HTTP "http://"
#define FTP "ftp://"
#define PROXYPORT 5001 //Proxy 端口
#define BUFSIZE 10240 //缓冲区大小

CWinApp theApp;
using namespace std;
UINT ProxyToServer(LPVOID pParam);
UINT UserToProxyThread(void *pParam);
struct SocketPair{
SOCKET user_proxy; //socket : 本地机器到PROXY 服务机
SOCKET proxy_server; //socket : PROXY 服务机到远程主机
BOOL IsUser_ProxyClosed; // 本地机器到PROXY 服务机状态
BOOL IsProxy_ServerClosed; // PROXY 服务机到远程主机状态
};

struct ProxyParam{
char Address[256]; // 远程主机地址
HANDLE User_SvrOK; // PROXY 服务机到远程主机的联结状态
SocketPair *pPair; // 维护一组SOCKET的指针
int Port; // 用来联结远程主机的端口
}; file://这个结构用来PROXY SERVER与远程主机的信息交换.
SOCKET gListen_Socket; file://用来侦听的SOCKET。
int StartServer() //启动服务
{
WSADATA wsaData;
sockaddr_in local;
SOCKET listen_socket;
if(::WSAStartup(0x202,&wsaData)!=0)
{printf("\nError in Startup session.\n");WSACleanup();return -1;};
local.sin_family=AF_INET;
local.sin_addr.s_addr=INADDR_ANY;
local.sin_port=htons(PROXYPORT);
listen_socket=socket(AF_INET,SOCK_STREAM,0);
if(listen_socket==INVALID_SOCKET)
{printf("\nError in New a Socket.");WSACleanup();return -2;}
if(::bind(listen_socket,(sockaddr *)&local,sizeof(local))!=0)
{printf("\n Error in Binding socket."); WSACleanup();return -3; };
if(::listen(listen_socket,5)!=0)
{printf("\n Error in Listen."); WSACleanup(); return -4;}
gListen_Socket=listen_socket;
AfxBeginThread(UserToProxyThread,NULL); //启动侦听
return 1;
}
int CloseServer() //关闭服务
{
closesocket(gListen_Socket);
WSACleanup();
return 1;
}
file://分析接收到的字符，得到远程主机地址
int GetAddressAndPort( char * str, char *address, int * port)
{
char buf[BUFSIZE], command[512], proto[128], *p;
int j;
sscanf(str,"%s%s%s",command,buf,proto);
p=strstr(buf,HTTP);
//HTTP
if(p)
{
p+=strlen(HTTP);
for(int i=0;i< strlen(p);i++)
if( *(p+i)==`/`) break;
*(p+i)=0;
strcpy(address,p);
p=strstr(str,HTTP);
for(int j=0;j< i+strlen(HTTP);j++)
*(p+j)=` `; //去掉远程主机名: GET http://www.njust.edu.cn/
HTTP1.1 == > GET / HTTP1.1
*port=80; //缺省的 http 端口
}
else
{//FTP, 不支持, 下面的代码可以省略.
p=strstr(buf,FTP);
if(!p) return 0;
p+=strlen(FTP);
for(int i=0;i< strlen(p);i++)
if( *(p+i)==`/`) break; //Get The Remote Host
*(p+i)=0;
for(j=0;j< strlen(p);j++)
if(*(p+j)==`:`)
{*port=atoi(p+j+1); //Get The Port
*(p+j)=0;
}
else *port=21;
strcpy(address,p);
p=strstr(str,FTP);
for(j=0;j< i+strlen(FTP);j++)
*(p+j)=` `;
}
return 1;
}
// 取到本地的数据，发往远程主机
UINT UserToProxyThread(void *pParam)
{
char Buffer[BUFSIZE];
int Len;
sockaddr_in from;
SOCKET msg_socket;
int fromlen,retval;
SocketPair SPair;
ProxyParam ProxyP;
CWinThread *pChildThread;
fromlen=sizeof(from);
msg_socket=accept(gListen_Socket,(struct sockaddr*)&from,&fromlen);
AfxBeginThread(UserToProxyThread,pParam); //启动另一侦听.
if( msg_socket==INVALID_SOCKET)
{ printf( "\nError in accept "); return -5;}
//读客户的第一行数据
SPair.IsUser_ProxyClosed=FALSE;
SPair.IsProxy_ServerClosed=TRUE;
SPair.user_proxy=msg_socket;
retval=recv(SPair.user_proxy,Buffer,sizeof(Buffer),0);
if(retval==SOCKET_ERROR)
{ printf("\nError Recv");
if(SPair.IsUser_ProxyClosed==FALSE)
{closesocket(SPair.user_proxy);
SPair.IsUser_ProxyClosed=TRUE;
}
}
if(retval==0)
{printf("Client Close connection\n");
if(SPair.IsUser_ProxyClosed==FALSE)
{closesocket(SPair.user_proxy);
SPair.IsUser_ProxyClosed=TRUE;
}
}
Len=retval;
#ifdef _DEBUG
Buffer[Len]=0;
printf("\n Received %d bytes,data[%s]from client\n",retval,Buffer);
#endif
//
SPair.IsUser_ProxyClosed=FALSE;
SPair.IsProxy_ServerClosed=TRUE;
SPair.user_proxy=msg_socket;
ProxyP.pPair=&SPair;
ProxyP.User_SvrOK=CreateEvent(NULL,TRUE,FALSE,NULL);
GetAddressAndPort( Buffer,ProxyP.Address,&ProxyP.Port);
pChildThread=AfxBeginThread(ProxyToServer,(LPVOID)&ProxyP);
::WaitForSingleObject(ProxyP.User_SvrOK,60000); //等待联结
::CloseHandle(ProxyP.User_SvrOK);
while(SPair.IsProxy_ServerClosed ==FALSE && SPair.IsUser_ProxyClosed==FALSE)
{
retval=send(SPair.proxy_server,Buffer,Len,0);
if(retval==SOCKET_ERROR)
{ printf("\n send() failed:error%d\n",WSAGetLastError());
if(SPair.IsProxy_ServerClosed==FALSE)
{
closesocket(SPair.proxy_server);
SPair.IsProxy_ServerClosed=TRUE;
}
continue;
}
retval=recv(SPair.user_proxy,Buffer,sizeof(Buffer),0);
if(retval==SOCKET_ERROR)
{ printf("\nError Recv");
if(SPair.IsUser_ProxyClosed==FALSE)
{closesocket(SPair.user_proxy);
SPair.IsUser_ProxyClosed=TRUE;
}
continue;
}
if(retval==0)
{printf("Client Close connection\n");
if(SPair.IsUser_ProxyClosed==FALSE)
{closesocket(SPair.user_proxy);
SPair.IsUser_ProxyClosed=TRUE;
}
break;
}
Len=retval;
#ifdef _DEBUG
Buffer[Len]=0;
printf("\n Received %d bytes,data[%s]from client\n",retval,Buffer);
#endif
} End While
if(SPair.IsProxy_ServerClosed==FALSE)
{
closesocket(SPair.proxy_server);
SPair.IsProxy_ServerClosed=TRUE;
}
if(SPair.IsUser_ProxyClosed==FALSE)
{closesocket(SPair.user_proxy);
SPair.IsUser_ProxyClosed=TRUE;
}
::WaitForSingleObject(pChildThread- >m_hThread,20000); //Should check the
return value
return 0;
}
// 读取远程主机数据，并发往本地客户机
UINT ProxyToServer(LPVOID pParam){
ProxyParam * pPar=(ProxyParam*)pParam;
char Buffer[BUFSIZE];
char *server_name= "localhost";
unsigned short port ;
int retval,Len;
unsigned int addr;
int socket_type ;
struct sockaddr_in server;
struct hostent *hp;
SOCKET conn_socket;
socket_type = SOCK_STREAM;
server_name = pPar- >Address;
port = pPar- >Port;
if (isalpha(server_name[0])) { /* server address is a name */
hp = gethostbyname(server_name);
}
else { /* Convert nnn.nnn address to a usable one */
addr = inet_addr(server_name);
hp = gethostbyaddr((char *)&addr,4,AF_INET);
}
if (hp == NULL ) {
fprintf(stderr,"Client: Cannot resolve address [%s]: Error %d\n",
server_name,WSAGetLastError());
::SetEvent(pPar- >User_SvrOK);
return 0;
}
//
// Copy the resolved information into the sockaddr_in structure
//
memset(&server,0,sizeof(server));
memcpy(&(server.sin_addr),hp- >h_addr,hp- >h_length);
server.sin_family = hp- >h_addrtype;
server.sin_port = htons(port);
conn_socket = socket(AF_INET,socket_type,0); /* 打开一个 socket */
if (conn_socket < 0 ) {
fprintf(stderr,"Client: Error Opening socket: Error %d\n",
WSAGetLastError());
pPar- >pPair- >IsProxy_ServerClosed=TRUE;
::SetEvent(pPar- >User_SvrOK);
return -1;
}

#ifdef _DEBUG
printf("Client connecting to: %s\n",hp- >h_name);
#endif
if (connect(conn_socket,(struct sockaddr*)&server,sizeof(server))
== SOCKET_ERROR) {
fprintf(stderr,"connect() failed: %d\n",WSAGetLastError());
pPar- >pPair- >IsProxy_ServerClosed=TRUE;
::SetEvent(pPar- >User_SvrOK);
return -1;
}
pPar- >pPair- >proxy_server=conn_socket;
pPar- >pPair- >IsProxy_ServerClosed=FALSE;
::SetEvent(pPar- >User_SvrOK);
// cook up a string to send
while(!pPar- >pPair- >IsProxy_ServerClosed &&!pPar- >pPair->IsUser_ProxyClosed)
{
retval = recv(conn_socket,Buffer,sizeof (Buffer),0 );
if (retval == SOCKET_ERROR ) {
fprintf(stderr,"recv() failed: error %d\n",WSAGetLastError());
closesocket(conn_socket);
pPar- >pPair- >IsProxy_ServerClosed=TRUE;
break;
}
Len=retval;
if (retval == 0) {
printf("Server closed connection\n");
closesocket(conn_socket);
pPar- >pPair- >IsProxy_ServerClosed=TRUE;
break;
}
retval = send(pPar- >pPair- >user_proxy,Buffer,Len,0);
if (retval == SOCKET_ERROR) {
fprintf(stderr,"send() failed: error %d\n",WSAGetLastError());
closesocket(pPar- >pPair- >user_proxy);
pPar- >pPair- >IsUser_ProxyClosed=TRUE;
break;
}
#ifdef _DEBUG
Buffer[Len]=0;
printf("Received %d bytes, data [%s] from server\n",retval,Buffer);
#endif
}
if(pPar- >pPair- >IsProxy_ServerClosed==FALSE)
{
closesocket(pPar- >pPair- >proxy_server);
pPar- >pPair- >IsProxy_ServerClosed=TRUE;
}
if(pPar- >pPair- >IsUser_ProxyClosed==FALSE)
{closesocket(pPar- >pPair- >user_proxy);
pPar- >pPair- >IsUser_ProxyClosed=TRUE;
}
return 1;
}

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
int nRetCode = 0;
// 初始化SOCKET
if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0))
{
// 错误处理
cerr < < _T("Fatal Error: MFC initialization failed") < < endl;
nRetCode = 1;
}
else
{
// 主程序开始.
StartServer();
while(1)
if(getchar()==`q`) break;
CloseServer();
}
return nRetCode;
}