设置InternetConnect的httpRequest连接数

这几天在写http断点下传的实现，遇到问题:

* 开多个httpConnect, 每个Connect对应一个httpRequest, 如果超过4个httpConnect, sendHttpRequest时，阻塞住了.

   只有前面的httpConnect任务完成后，被阻塞线程的sendHttpRequest才返回.

 

* 如果是下载不同服务器的文件, 则不会出现sendHttpRequest阻塞.

 

同事在stackoverflow上找到资料, 可以设置连接同一个服务器httpConnect的连接数为指定值，解决了这个问题。

整理一下。

HINTERNET   FCHttpRequest::create_connect()
{
    std::wstring        strTemp = L"";
    HINTERNET           hConnect = NULL;
    INTERNET_PORT       nPort = INTERNET_DEFAULT_HTTP_PORT;
    CLsStopWatchTick    watch;

    if (m_tmp_scheme == INTERNET_SCHEME_HTTPS)
    {
        nPort = INTERNET_DEFAULT_HTTPS_PORT;
    }

    watch.start();
    hConnect = InternetConnect(m_http_session.GetHandle(), m_tmp_host.c_str(), nPort, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 0);
    strTemp = ns_base::StringFormatV(
        L"create_connect() : [FCHttpRequest = 0x%p][TID = %d] : hConnect = 0x%p\r\n", 
        this,
        ::GetCurrentThreadId(),
        hConnect);
    watch.StopAndShow(strTemp.c_str(), TRUE);

    if (NULL != hConnect)
    {
        /// 试验过了, 在程序开始设置 HINTERNE 为NULL, 那种http连接数, 是没用的
        /// 只有在InternetConnect 所在线程中, 对有效httpConnect设置指定连接数, 才有效
        SetHttpMaxConnectNumberEx(hConnect);
    }

    return hConnect;
}

void FCHttpRequest::SetHttpMaxConnectNumberEx(HINTERNET hHandle)
{
    BOOL    bRc = FALSE;
    DWORD   dwErr = 0;
    DWORD   dwHttpConnectMax = 50/*5 * 5 * 2 + 10*/; ///< (5条任务，一个任务5条线程) * 2 + 10(备用数目)

    DWORD   dwRecvBufLen = 0;

    BOOL    bRcOld = FALSE;
    DWORD   dwHttpConnectOld = 0;   ///< INTERNET_OPTION_MAX_CONNS_PER_SERVER's cnt

    BOOL    bRcOld10 = FALSE;
    DWORD   dwHttpConnectOld10 = 0; ///< INTERNET_OPTION_MAX_CONNS_PER_1_0_SERVER's cnt

    dwHttpConnectOld = 0;
    bRc = GetHttpMaxConnectNumberEx(hHandle, INTERNET_OPTION_MAX_CONNS_PER_SERVER, dwHttpConnectOld);
    dwErr = ::GetLastError();
    _ASSERT(bRc);

    dwHttpConnectOld10 = 0;
    bRc = GetHttpMaxConnectNumberEx(hHandle, INTERNET_OPTION_MAX_CONNS_PER_1_0_SERVER, dwHttpConnectOld10);
    dwErr = ::GetLastError();
    _ASSERT(bRc);

    /// 设置不成功, 设置成功的，取出来还是原来的值.
    bRc = InternetSetOption(hHandle,INTERNET_OPTION_MAX_CONNS_PER_SERVER,&dwHttpConnectMax,sizeof(DWORD));
    dwErr = ::GetLastError();
//    _ASSERT(bRc); ///< 虽然为FALSE, 但是已经有效果了

    bRc = InternetSetOption(hHandle,INTERNET_OPTION_MAX_CONNS_PER_1_0_SERVER,&dwHttpConnectMax,sizeof(DWORD));
    dwErr = ::GetLastError();
//    _ASSERT(bRc);  ///< 虽然为FALSE, 但是已经有效果了

    /// 这里得到的连接数, 也是旧的, 但是从程序运行效果上看，已经生效了
    dwHttpConnectOld = 0;
    bRc = GetHttpMaxConnectNumberEx(hHandle, INTERNET_OPTION_MAX_CONNS_PER_SERVER, dwHttpConnectOld);
    dwErr = ::GetLastError();
    _ASSERT(bRc);

    /// 这里得到的连接数, 也是旧的, 但是从程序运行效果上看，已经生效了
    dwHttpConnectOld10 = 0;
    bRc = GetHttpMaxConnectNumberEx(hHandle, INTERNET_OPTION_MAX_CONNS_PER_1_0_SERVER, dwHttpConnectOld10);
    dwErr = ::GetLastError();
    _ASSERT(bRc);
}

BOOL FCHttpRequest::GetHttpMaxConnectNumberEx(HINTERNET hHandle, DWORD dwOption, DWORD& dwCnt)
{
    BOOL    bRc = FALSE;
    DWORD   dwRecvBufLen = 0;

    dwCnt = 0;
    bRc = InternetQueryOption(
        NULL, 
        dwOption, 
        NULL, 
        &dwRecvBufLen);

    if (!bRc)
    {
        _ASSERT(dwRecvBufLen == sizeof(DWORD));
        bRc = ::InternetQueryOption(
            NULL, 
            dwOption,
            (LPVOID)&dwCnt, 
            &dwRecvBufLen);
        _ASSERT(bRc);
    }

    return bRc;
}