SOCKET通过代理连接服务器

代理方式包括：HTTP代理、SOCKET5代理。RFC参考文档：http://oss.org.cn/man/develop/rfc/default.htm
一、通过HTTP代理

int CProxy_TestDlg::HttpConnect(const char *proxy_ip,int proxy_port,const char *svr_ip,int svr_port)
{
    SOCKET socket_ = ::socket(AF_INET,SOCK_STREAM,0);
    sockaddr_in sa;
    sa.sin_addr.s_addr = inet_addr(proxy_ip);
    sa.sin_port = htons(proxy_port);
    sa.sin_family = AF_INET;

    int error_code = ::connect(socket_,(SOCKADDR*)&sa,sizeof(sa));  
    if(error_code == SOCKET_ERROR)  
    {  
        ::closesocket(socket_);
        return 1;  
    }  
    char tmpBuffer[128] = {0};
    ::sprintf(tmpBuffer,"CONNECT %s:%d HTTP/1.1
User-Agent: Mozilla/4.0
Connection: Keep-Alive

",svr_ip,svr_port);
    ::send(socket_,tmpBuffer,strlen(tmpBuffer),0);  
    memset(tmpBuffer,0,128);
    ::recv(socket_,tmpBuffer,128,0); 
    int mj, mi, code;
    ::sscanf(tmpBuffer, "HTTP/%d.%d %d", &mj, &mi, &code);
    if (code != 200)
    { 
        ::closesocket(socket_);
        return 2;
    }
    ::closesocket(socket_);
    return 0;
}

HTTP代理方式测试通过。。。
二、SOCKET5代理
1、使用的结构如下：

#pragma pack(push,1)
//请求认证方式
typedef struct tagSocket5_Requst
{
    char Ver;            //版本号:05
    char NMethods;
    char Methods[255];
}Socket5_Request,*LPSocket5_Request;
//认证方式应答
typedef struct tagSocket5_Response
{
    char Ver;
    char Method;//X'00'不需要认证;X'01'GSSAPI;X'02用户名/密码;X'03' -- X'7F'由IANA分配;X'80' -- X'FE'为私人方法所保留的;X'FF'没有可以接受的方法

}Socket5_Response,*LPSocket5_Response;

//认证请求
typedef struct tagSocket5_Auth_Request
{
    char   Ver;   //1 
    char   Ulen;    
    char   Name[255];    
    char   PLen;    
    char   Pass[255];
}Socket5_Auth_Request,*LPSocket5_Auth_Request;

typedef struct tagSocket5_Auth_Response
{  
    char   Ver;    
    char   Status; 
}Socket5_Auth_Response,*LPSocket5_Auth_Response;
//连接请求
typedef struct tagSocket5_Connect_Request
{
    char Ver;
    char Cmd;//CONNECT：X'01';BIND：X'02';UDP ASSOCIATE：X'03'
    char Rsv;//保留，填0
    char Atyp;//   后面的地址类型,IPV4：X'01';域名：X'03';IPV6：X'04',暂时只支持IPV4
    unsigned long DestAddr;//IPV4是4个字节，IPV6是6个字节;基于域名的地址，地址字段中的第一字节是以字节为单位的该域名的长度，没有结尾的NUL字
    unsigned short DestPort;

}Sokcet5_Connect_Request,*LPSocket5_Connect_Request;
//连接应答
typedef struct tagSokcet5_Connect_Response
{
    char Ver;
    char Rep;
    char Rsv;
    char Atyp;
    unsigned long DestAddr;
    unsigned short DestPort;
}Socket5_Connect_Response,*LPSocket5_Connect_Response;
#pragma pack(pop)
2、函数定义：
int CProxy_TestDlg::Socket5Connect(const char *proxy_ip,int proxy_port,const char *user,const char *passwd,const char *svr_ip,int svr_port)
{
    //首先连接SOCKET5代理服务器
    SOCKET socket_ = ::socket(AF_INET,SOCK_STREAM,0);
    sockaddr_in sa;
    sa.sin_addr.s_addr = inet_addr(proxy_ip);
    sa.sin_port = htons(proxy_port);
    sa.sin_family = AF_INET;

    int error_code = ::connect(socket_,(SOCKADDR*)&sa,sizeof(sa));  
    if(error_code == SOCKET_ERROR)  
    {  
        ::closesocket(socket_);
        return 1;  
    }  
    char buffer[128] = {0};
    int len = 0;
    //发送认证发送请求Socket5_Request/Socket5_Response
    Socket5_Request req;
    Socket5_Response rep;
    req.Ver = 0x05;
    req.NMethods = 2;
    req.Methods[0] = 0;
    req.Methods[1] = 2;
    if((len = ::send(socket_,(char*)&req,sizeof(req),0)) <=0)
    {
        ::closesocket(socket_);
        return 4;
    }

    if((len = ::recv(socket_,(char*)&rep,sizeof(rep),0)) <=0)
    {
        ::closesocket(socket_);
        return 4;
    }

    if(rep.Ver != 0x05)
    {
        ::closesocket(socket_);
        return 5;
    }

    if(rep.Method != 0x00 && rep.Method != 0x02)
    {
        ::closesocket(socket_);
        return 6;
    }

    if(rep.Method == 0x02)
    {//需要用户名、密码验证
    
        //进行认证Socket5_Auth_Request/Socket5_Auth_Response
        Socket5_Auth_Request auth_req;
        Socket5_Auth_Response auth_rep;
        memset(&auth_req,0,sizeof(Socket5_Auth_Request));
        memset(&auth_rep,0,sizeof(Socket5_Auth_Response));
        auth_req.Ver = 1;//?
        auth_req.Ulen = strlen(user);
        strcpy(auth_req.Name,user);
        auth_req.PLen = strlen(passwd);
        strcpy(auth_req.Pass,passwd);
        if((len = ::send(socket_,(char*)&auth_req,sizeof(auth_req),0)) <=0)
        {
            ::closesocket(socket_);
            return 4;
        }
        if((len = ::recv(socket_,(char*)&auth_rep,sizeof(auth_rep),0)) <=0)
        {
            ::closesocket(socket_);
            return 4;
        }
        if(auth_rep.Status != 0)
        {
            ::closesocket(socket_);
            return 7;
        }
    }
    //发送连接请求Sokcet5_Connect_Request/Socket5_Connect_Response
    Sokcet5_Connect_Request conn_req;
    Socket5_Connect_Response conn_rep;
    memset(&conn_req,0,sizeof(Sokcet5_Connect_Request));
    memset(&conn_rep,0,sizeof(Socket5_Connect_Response));

    conn_req.Ver = 0x05;
    conn_req.Cmd = 0x01;//
    conn_req.Atyp = 0x01;
    conn_req.DestAddr = inet_addr(svr_ip);
    conn_req.DestPort = htons(svr_port);

    if((len = ::send(socket_,(char*)&conn_req,sizeof(conn_req),0)) <=0)
    {
        ::closesocket(socket_);
        return 4;
    }

    if((len = ::recv(socket_,(char*)&conn_rep,sizeof(conn_rep),0)) <=0)
    {
        ::closesocket(socket_);
        return 4;
    }
    if(conn_rep.Rep != 0)
    {
        ::closesocket(socket_);
        return 8;
    }
    //连接成功

    ::closesocket(socket_);
    return 0;
}

SOCKET5还没有测试。。。
三、根据网址获取该网址的IP地址
char * URL2IP(const char *url)
{
    struct hostent * ph;
    struct in_addr in;
    memset( &in, 0x0, sizeof(in) );
    // 传递的域名地址通过 gethostbyname 函数转换成 HOSTENT 结构的指针
    if((ph = gethostbyname(url)) == NULL)
        return NULL;

    memcpy( (char**)&in, ph->h_addr_list[0], sizeof(in) );

    return ::inet_ntoa( in ); 
}