C++ Programming Notes: Use WinHTTP to achieve HTTP access (solve the problem of receiving UTF8 data garbled)

The process of implementing HTTP access includes the following steps: 
1. First, we open a Session to get a HINTERNET session handle; 
2. Then we use this session handle to connect to the server to get a HINTERNET connect handle; 
3. Then we use this connect handle to open Http request gets a HINTERNET request handle; 
4. At this time, we can use this request handle to send data and read the data returned from the server; 
5. Finally, close the request, connect, and session handles in turn.

Microsoft provides two sets of http access interfaces: WinHTTP and WinINet. WinHTTP is more secure and robust than WinINet, and it can be considered that WinHTTP is an upgraded version of WinINet. These two APIs contain many similar functions and macro definitions, and the access process is completely similar (the above 5 steps). This article mainly implements the post request method through WinHTTP, and explains it strictly in accordance with the above five steps. 
And because the data I received was UTF8 instead of ASCII, the data I received at the beginning was garbled. In the following code, I will explain in detail the cause of the garbled code and how to solve it. 
Okay, Xiao Er, go to the code!
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#include "stdafx.h"
#include "jsonparser.h"

#include <string>
#include <windows.h>
#include <winhttp.h>
#pragma comment(lib, "winhttp.lib")



int _tmain(int argc, _TCHAR* argv[])
{
    HINTERNET hSession = NULL;
    HINTERNET hConnect = NULL;
    HINTERNET hRequest = NULL;

    //1. 初始化一个WinHTTP-session句柄，参数1为此句柄的名称
    hSession = WinHttpOpen(L"csdn@elaine_bao", NULL, NULL, NULL, NULL);
    if (hSession == NULL) {
        cout<<"Error:Open session failed: "<<GetLastError()<<endl;
        return -1;
    }

    //2. 通过上述句柄连接到服务器，需要指定服务器IP和端口号。若连接成功，返回的hConnect句柄不为NULL
    hConnect = WinHttpConnect(hSession, L"192.168.50.112", (INTERNET_PORT)8080, 0);
    if (hConnect == NULL) {
        cout << "Error:Connect failed: " << GetLastError()<<endl;
        return -1;
    }

    //3. 通过hConnect句柄创建一个hRequest句柄，用于发送数据与读取从服务器返回的数据。
    hRequest = WinHttpOpenRequest(hConnect, L"Post", L"getServiceInfo", NULL, WINHTTP_NO_REFERER, WINHTTP_DEFAULT_ACCEPT_TYPES, 0);
    //其中参数2表示请求方式，此处为Post；参数3:给定Post的具体地址，如这里的具体地址为http://192.168.50.112/getServiceInfo
    if (hRequest == NULL) {
        cout << "Error:OpenRequest failed: " << GetLastError() << endl;
        return -1;
    }

    //4-1. 向服务器发送post数据
    //(1) 指定发送的数据内容
    string data = "This is my data to be sent"; 
    const void *ss = (const char *)data.c_str();

    //(2) 发送请求
    BOOL bResults;
    bResults = WinHttpSendRequest(hRequest, WINHTTP_NO_ADDITIONAL_HEADERS, 0, const_cast<void*>(ss), data.length(), data.length(), 0);
    if (!bResults){
        cout << "Error:SendRequest failed: " << GetLastError() << endl;
        return -1;
    }
    else{
        //（3） 发送请求成功则准备接受服务器的response。注意：在使用 WinHttpQueryDataAvailable和WinHttpReadData前必须使用WinHttpReceiveResponse才能access服务器返回的数据
        bResults = WinHttpReceiveResponse(hRequest, NULL);
    }

    //4-2. 获取服务器返回数据的header信息。这一步我用来获取返回数据的数据类型。
    LPVOID lpHeaderBuffer = NULL;
    DWORD dwSize = 0;   
    if (bResults)
    {
        //(1) 获取header的长度
        WinHttpQueryHeaders(hRequest, WINHTTP_QUERY_RAW_HEADERS_CRLF,
            WINHTTP_HEADER_NAME_BY_INDEX, NULL,
            &dwSize, WINHTTP_NO_HEADER_INDEX);

        //(2) 根据header的长度为buffer申请内存空间
        if (GetLastError() == ERROR_INSUFFICIENT_BUFFER)
        {
            lpHeaderBuffer = new WCHAR[dwSize / sizeof(WCHAR)];

            //(3) 使用WinHttpQueryHeaders获取header信息
            bResults = WinHttpQueryHeaders(hRequest,
                WINHTTP_QUERY_RAW_HEADERS_CRLF,
                WINHTTP_HEADER_NAME_BY_INDEX,
                lpHeaderBuffer, &dwSize,
                WINHTTP_NO_HEADER_INDEX);
        }
    }
    printf("Header contents: \n%S", lpHeaderBuffer);

    //解析上述header信息会发现服务器返回数据的charset为uft-8。这意味着后面需要对获取到的raw data进行宽字符转换。一开始由于没有意识到需要进行转换所以得到的数据都是乱码。
    //出现乱码的原因是：HTTP在传输过程中是二值的，它并没有text或者是unicode的概念。HTTP使用7bit的ASCII码作为HTTP headers，但是内容是任意的二值数据，需要根据header中指定的编码方式来描述它（通常是Content-Type header）.
    //因此当你接收到原始的HTTP数据时，先将其保存到char[] buffer中，然后利用WinHttpQueryHearders()获取HTTP头，得到内容的Content-Type,这样你就知道数据到底是啥类型的了，是ASCII还是Unicode或者其他。
    //一旦你知道了具体的编码方式，你就可以通过MultiByteToWideChar()将其转换成合适编码的字符，存入wchar_t[]中。
    //关于乱码的解决方案请看4-4

    //4-3. 获取服务器返回数据
    LPSTR pszOutBuffer = NULL;
    DWORD dwDownloaded = 0;         //实际收取的字符数
    wchar_t *pwText = NULL;
    if (bResults)
    {
        do
        {
            //(1) 获取返回数据的大小（以字节为单位）
            dwSize = 0;
            if (!WinHttpQueryDataAvailable(hRequest, &dwSize)){
                cout << "Error：WinHttpQueryDataAvailable failed：" << GetLastError() << endl;
                break;
            }           
            if (!dwSize)    break;  //数据大小为0                

            //(2) 根据返回数据的长度为buffer申请内存空间
            pszOutBuffer = new char[dwSize + 1];
            if (!pszOutBuffer){
                cout<<"Out of memory."<<endl;
                break;
            }
            ZeroMemory(pszOutBuffer, dwSize + 1);       //将buffer置0

            //(3) 通过WinHttpReadData读取服务器的返回数据
            if (!WinHttpReadData(hRequest,pszOutBuffer, dwSize, &dwDownloaded)){
                cout << "Error：WinHttpQueryDataAvailable failed：" << GetLastError() << endl;
            }
            if (!dwDownloaded)
                break;

        } while (dwSize > 0);

        //4-4. 将返回数据转换成UTF8
        DWORD dwNum = MultiByteToWideChar(CP_ACP, 0, pszOutBuffer, -1, NULL, 0);    //返回原始ASCII码的字符数目       
        pwText = new wchar_t[dwNum];                                                //根据ASCII码的字符数分配UTF8的空间
        MultiByteToWideChar(CP_UTF8, 0, pszOutBuffer, -1, pwText, dwNum);           //将ASCII码转换成UTF8
        printf("Received contents: \n%S", pwText);
    }


    //5. 依次关闭request，connect，session句柄
    if (hRequest) WinHttpCloseHandle(hRequest);
    if (hConnect) WinHttpCloseHandle(hConnect);
    if (hSession) WinHttpCloseHandle(hSession);


    return 0;
}