本文无实质性创新性内容，性质属于技术总结，内容是基于已有知识或定义的代码实现。文中的代码是我根据其他代码或者网络上的资料，写出的自己的版本。因为网络上的代码 C/C++ 版本的较少，或者本身不一定是最合适最容易使用的。所以我写的代码基本是以 C 语言和 C 字符串处理为主的，因此它也可以直接在 C++ 的项目中使用。
（1）Base64 编码。Base64 编码是把每 3 个字节转换成 4 个ascii 字符（根据字符表映射）。把文本编码后，对人来说难以直接阅读。结尾不足时可能有一到两个 "=" 字符的补齐。

code_Base64
//以下是 Base64.h 的内容:
size_t Base64_Decode(char *pDest, const char *pSrc, size_t srclen);
size_t Base64_Encode(char *pDest, const char *pSrc, size_t srclen);
//以下是 Base64.cpp 的内容:
BYTE Decode_GetByte(char c);
char Encode_GetChar(BYTE num);
//===================================
//    Base64 解码
//===================================
BYTE Decode_GetByte(char c)
{
    if(c == '+')
        return 62;
    else if(c == '/')
        return 63;
    else if(c <= '9')
        return (BYTE)(c - '0' + 52);
    else if(c == '=')
        return 64;
    else if(c <= 'Z')
        return (BYTE)(c - 'A');
    else if(c <= 'z')
        return (BYTE)(c - 'a' + 26);
    return 64;
}
//解码
size_t Base64_Decode(char *pDest, const char *pSrc, size_t srclen)
{
    BYTE input[4];
    size_t i, index = 0;
    for(i = 0; i < srclen; i += 4)
    {
        //byte[0]
        input[0] = Decode_GetByte(pSrc[i]);
        input[1] = Decode_GetByte(pSrc[i + 1]);
        pDest[index++] = (input[0] << 2) + (input[1] >> 4);
        
        //byte[1]
        if(pSrc[i + 2] != '=')
        {
            input[2] = Decode_GetByte(pSrc[i + 2]);
            pDest[index++] = ((input[1] & 0x0f) << 4) + (input[2] >> 2);
        }
        //byte[2]
        if(pSrc[i + 3] != '=')
        {
            input[3] = Decode_GetByte(pSrc[i + 3]);
            pDest[index++] = ((input[2] & 0x03) << 6) + (input[3]);
        }            
    }
    //null-terminator
    pDest[index] = 0;
    return index;
}
//===================================
//    Base64 编码
//===================================
char Encode_GetChar(BYTE num)
{
    return 
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "abcdefghijklmnopqrstuvwxyz"
        "0123456789"
        "+/="[num];
}
//编码
size_t Base64_Encode(char *pDest, const char *pSrc, size_t srclen)
{
    BYTE input[3], output[4];
    size_t i, index_src = 0, index_dest = 0;
    for(i = 0; i < srclen; i += 3)
    {
        //char [0]
        input[0] = pSrc[index_src++];
        output[0] = (BYTE)(input[0] >> 2);
        pDest[index_dest++] = Encode_GetChar(output[0]);
        //char [1]
        if(index_src < srclen)
        {
            input[1] = pSrc[index_src++];
            output[1] = (BYTE)(((input[0] & 0x03) << 4) + (input[1] >> 4));
            pDest[index_dest++] = Encode_GetChar(output[1]);
        }
        else
        {
            output[1] = (BYTE)((input[0] & 0x03) << 4);
            pDest[index_dest++] = Encode_GetChar(output[1]);
            pDest[index_dest++] = '=';
            pDest[index_dest++] = '=';
            break;
        }
        
        //char [2]
        if(index_src < srclen)
        {
            input[2] = pSrc[index_src++];
            output[2] = (BYTE)(((input[1] & 0x0f) << 2) + (input[2] >> 6));
            pDest[index_dest++] = Encode_GetChar(output[2]);
        }
        else
        {
            output[2] = (BYTE)((input[1] & 0x0f) << 2);
            pDest[index_dest++] = Encode_GetChar(output[2]);
            pDest[index_dest++] = '=';
            break;
        }
        //char [3]
        output[3] = (BYTE)(input[2] & 0x3f);
        pDest[index_dest++] = Encode_GetChar(output[3]);
    }
    //null-terminator
    pDest[index_dest] = 0;
    return index_dest;
}

（2）UrlEncode （百分号编码）。方法是把输入的字符串先用 UTF-8 编码，然后把基本字符以外的字节用百分号加16进制的形式编码。UrlEncode 的最后一个参数含义是，编码结果中的16进制字符是否采用大写字母表示。

BOOL UrlEncode(const char* szSrc, char* pBuf, int cbBufLen, BOOL bUpperCase);
BOOL UrlDecode(const char* szSrc, char* pBuf, int cbBufLen);
//百分号编码
//http://zh.wikipedia.org/zh-cn/%E7%99%BE%E5%88%86%E5%8F%B7%E7%BC%96%E7%A0%81
BOOL UrlEncode(const char* szSrc, char* pBuf, int cbBufLen, BOOL bUpperCase)
{
    if(szSrc == NULL || pBuf == NULL || cbBufLen <= 0)
        return FALSE;
    size_t len_ascii = strlen(szSrc);
    if(len_ascii == 0)
    {
        pBuf[0] = 0;
        return TRUE;
    }
    
    //先转换到UTF-8
    char baseChar = bUpperCase ? 'A' : 'a';
    int cchWideChar = MultiByteToWideChar(CP_ACP, 0, szSrc, len_ascii, NULL, 0);
    LPWSTR pUnicode = (LPWSTR)malloc((cchWideChar + 1) * sizeof(WCHAR));
    if(pUnicode == NULL)
        return FALSE;
    MultiByteToWideChar(CP_ACP, 0, szSrc, len_ascii, pUnicode, cchWideChar + 1);
    int cbUTF8 = WideCharToMultiByte(CP_UTF8, 0, pUnicode, cchWideChar, NULL, 0, NULL, NULL);
    LPSTR pUTF8 = (LPSTR)malloc((cbUTF8 + 1) * sizeof(CHAR));
    if(pUTF8 == NULL)
    {
        free(pUnicode);
        return FALSE;
    }
    WideCharToMultiByte(CP_UTF8, 0, pUnicode, cchWideChar, pUTF8, cbUTF8 + 1, NULL, NULL);
    pUTF8[cbUTF8] = '\0';
    unsigned char c;
    int cbDest = 0; //累加
    unsigned char *pSrc = (unsigned char*)pUTF8;
    unsigned char *pDest = (unsigned char*)pBuf;
    while(*pSrc && cbDest < cbBufLen - 1)
    {
        c = *pSrc;
        if(isalpha(c) || isdigit(c) || c == '-' || c == '.' || c == '~')
        {
            *pDest = c;
            ++pDest;
            ++cbDest;
        }
        else if(c == ' ')
        {
            *pDest = '+';
            ++pDest;
            ++cbDest;
        }
        else
        {
            //检查缓冲区大小是否够用？
            if(cbDest + 3 > cbBufLen - 1)
                break;
            pDest[0] = '%';
            pDest[1] = (c >= 0xA0) ? ((c >> 4) - 10 + baseChar) : ((c >> 4) + '0');
            pDest[2] = ((c & 0xF) >= 0xA)? ((c & 0xF) - 10 + baseChar) : ((c & 0xF) + '0');
            pDest += 3;
            cbDest += 3;
        }
        ++pSrc;
    }
    //null-terminator
    *pDest = '\0';
    free(pUnicode);
    free(pUTF8);
    return TRUE;
}
//解码后是utf-8编码
BOOL UrlDecode(const char* szSrc, char* pBuf, int cbBufLen)
{
    if(szSrc == NULL || pBuf == NULL || cbBufLen <= 0)
        return FALSE;
    size_t len_ascii = strlen(szSrc);
    if(len_ascii == 0)
    {
        pBuf[0] = 0;
        return TRUE;
    }
    
    char *pUTF8 = (char*)malloc(len_ascii + 1);
    if(pUTF8 == NULL)
        return FALSE;
    int cbDest = 0; //累加
    unsigned char *pSrc = (unsigned char*)szSrc;
    unsigned char *pDest = (unsigned char*)pUTF8;
    while(*pSrc)
    {
        if(*pSrc == '%')
        {
            *pDest = 0;
            //高位
            if(pSrc[1] >= 'A' && pSrc[1] <= 'F')
                *pDest += (pSrc[1] - 'A' + 10) * 0x10;
            else if(pSrc[1] >= 'a' && pSrc[1] <= 'f')
                *pDest += (pSrc[1] - 'a' + 10) * 0x10;
            else
                *pDest += (pSrc[1] - '0') * 0x10;
            //低位
            if(pSrc[2] >= 'A' && pSrc[2] <= 'F')
                *pDest += (pSrc[2] - 'A' + 10);
            else if(pSrc[2] >= 'a' && pSrc[2] <= 'f')
                *pDest += (pSrc[2] - 'a' + 10);
            else
                *pDest += (pSrc[2] - '0');
            pSrc += 3;
        }
        else if(*pSrc == '+')
        {
            *pDest = ' ';
            ++pSrc;
        }
        else
        {
            *pDest = *pSrc;
            ++pSrc;
        }
        ++pDest;
        ++cbDest;
    }
    //null-terminator
    *pDest = '\0';
    ++cbDest;
    int cchWideChar = MultiByteToWideChar(CP_UTF8, 0, (LPCSTR)pUTF8, cbDest, NULL, 0);
    LPWSTR pUnicode = (LPWSTR)malloc(cchWideChar * sizeof(WCHAR));
    if(pUnicode == NULL)
    {
        free(pUTF8);
        return FALSE;
    }
    MultiByteToWideChar(CP_UTF8, 0, (LPCSTR)pUTF8, cbDest, pUnicode, cchWideChar);
    WideCharToMultiByte(CP_ACP, 0, pUnicode, cchWideChar, pBuf, cbBufLen, NULL, NULL);
    free(pUTF8);
    free(pUnicode);
    return TRUE;
}

（3）获取本机 IP 地址和网卡物理地址。可能有多个网络适配器，但这里只是给出第一个适配器的结果。根据网络资料，获取网卡物理地址有多种方法。已知 IP 地址获取其物理地址可以使用 SendARP 方法。但对于本机来说，可以直接用 GetAdaptersAddresses 更适合，其返回结果为链表（list）形式。这里对 IP 默认为 IPv4（4个字节），网卡物理地址通常为 6 个字节。

#include <Winsock2.h>
#include <IPHlpApi.h> //for GetAdaptersAddresses
//获取本机的IP地址
BOOL GetIPAddress(unsigned char* buffer)
{
    int bRet;
    char hostname[256];
    WSADATA wsadata; 
    struct hostent *pHost;
    struct in_addr *pAddr;
    WORD dwVersionRequested = MAKEWORD( 2, 2 );
    
    bRet= WSAStartup(dwVersionRequested, &wsadata);
    bRet= gethostname(hostname, sizeof(hostname));
    pHost = gethostbyname(hostname);
    if(pHost != NULL && pHost->h_addr_list[0] != NULL) 
    {
        pAddr = (struct in_addr*)(pHost->h_addr_list[0]);
        buffer[0] = pAddr->s_net;
        buffer[1] = pAddr->s_host;
        buffer[2] = pAddr->s_lh;
        buffer[3] = pAddr->s_impno;
        bRet = TRUE;
    }
    else
    {
        //取不到IP地址，则赋值默认值 255.255.255.255
        memset(buffer, 0xff, 4);
        bRet = FALSE;
    }
    WSACleanup();
    return bRet;
}
//参数pMacAddr应该是8个字节的数组
BOOL GetMacAddress(unsigned char* pMacAddr)
{
    DWORD nRet;
    //只查询物理地址
    DWORD nFlags = GAA_FLAG_SKIP_UNICAST 
        | GAA_FLAG_SKIP_ANYCAST
        | GAA_FLAG_SKIP_FRIENDLY_NAME
        | GAA_FLAG_SKIP_MULTICAST
        | GAA_FLAG_SKIP_DNS_SERVER;
    ULONG bufLen = 1024;
    PIP_ADAPTER_ADDRESSES pAdapterAddr = (PIP_ADAPTER_ADDRESSES)malloc(bufLen);
    if(pAdapterAddr == NULL)
        return FALSE;
    //AF_INET: return only IPv4 addresses.
    nRet = GetAdaptersAddresses(AF_INET, nFlags,  NULL, pAdapterAddr, &bufLen);
    if(nRet == ERROR_BUFFER_OVERFLOW)
    {
        pAdapterAddr = (PIP_ADAPTER_ADDRESSES)realloc(pAdapterAddr, bufLen);
        if(pAdapterAddr == NULL)
            return FALSE;
        nRet = GetAdaptersAddresses(AF_INET, nFlags,  NULL, pAdapterAddr, &bufLen);
    }
    if(nRet == ERROR_SUCCESS)
    {
        memcpy(pMacAddr, &pAdapterAddr->PhysicalAddress, pAdapterAddr->PhysicalAddressLength);
        free(pAdapterAddr);
        return TRUE;
    }
    else
    {
        //ff-ff-ff-ff-ff-ff: 表示获取失败（未知）
        memset(pMacAddr, 0xff, 6);
        free(pAdapterAddr);
        return FALSE;
    }
}

（4）使用 SMTP 发送邮件。本文是参考看雪论坛上某文章中的代码。如果发送中文，应该在传输时，指定文本使用的编码，以防止接收端解释成乱码。以下代码引用了（1）中的 Base64 编码。

#include <Winsock2.h>
typedef struct _SMTPINFO
{
    char Server[32];
    int Port;
    char UserName[16];
    char Password[16];
    char From[32];
    char To[32];
    char Subject[32];
    char Msg[256];
} SMTPINFO, *LPSMTPINFO;

BOOL Talk(SOCKET sockid, const char *szOkCode, char *pSend);
BOOL SendMail(const LPSMTPINFO pInfo);
//szOkCode: 是前一条命令成功时，预期的服务器的返回码
BOOL Talk(SOCKET sockid, const char *szOkCode, char *pSend)
{
    const int buflen = 256;
    char buf[buflen];
    //接收返回信息
    if (recv(sockid, buf, buflen, 0) == SOCKET_ERROR)
        return FALSE;
    if (strncmp(buf, szOkCode, strlen(szOkCode)) != 0)
        return FALSE;
    //发送命令
    if (lstrlen(pSend) > 0)
    {
        WSABUF DataBuf;
        DataBuf.len = lstrlen(pSend);
        DataBuf.buf = pSend;
        DWORD dwS;
        if(WSASend(sockid, &DataBuf, 1, &dwS, 0, 0, 0))
            return FALSE;
    }
    return TRUE;
}
BOOL SendMail(const LPSMTPINFO pInfo)
{
    char buf[1024];
    //准备网络连接
    WSADATA wsadata;
    if(WSAStartup(MAKEWORD(2, 2), &wsadata) != 0)
        return FALSE;
    //创建套接字
    SOCKET sockid;
    if ((sockid = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
    {
        WSACleanup();
        return FALSE;
    }
    //得到smtp服务器ip
    struct hostent *phostent = gethostbyname(pInfo->Server);
    struct sockaddr_in addr;
    CopyMemory(&addr.sin_addr.S_un.S_addr,
        phostent->h_addr_list[0],
        sizeof(addr.sin_addr.S_un.S_addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(pInfo->Port);
    ZeroMemory(&addr.sin_zero, 8);
    //连接服务器
    if(connect(sockid, (struct sockaddr *)&addr, sizeof(struct sockaddr_in)) == SOCKET_ERROR)
        goto STOP;
    //EHLO 是对 HELO 的扩充命令。
    strcpy(buf, "EHLO hoodlum1980\r\n");
    if(!Talk(sockid, "220", buf))
        goto STOP;
    strcpy(buf, "AUTH LOGIN\r\n");
    if(!Talk(sockid, "250", buf))
        goto STOP;
    size_t userlen = lstrlen(pInfo->UserName);
    size_t passlen = lstrlen(pInfo->Password);
    Base64_Encode(buf, pInfo->UserName, userlen);
    strcat(buf, "\r\n");
    if(!Talk(sockid, "334", buf))
        goto STOP;
    Base64_Encode(buf, pInfo->Password, passlen);
    strcat(buf, "\r\n");
    if (!Talk(sockid, "334", buf))
        goto STOP;
    //ZeroMemory(buf, buflen);
    wsprintf(buf, "MAIL FROM:<%s>\r\n", pInfo->From);
    if(!Talk(sockid, "235", buf))
        goto STOP;
    wsprintf(buf, "RCPT TO:<%s>\r\n", pInfo->To);
    if(!Talk(sockid, "250", buf))
        goto STOP;
    strcpy(buf, "DATA\r\n");
    if (!Talk(sockid, "250", buf))
        goto STOP;
    char szContent[512];
    Base64_Encode(szContent, pInfo->Msg, strlen(pInfo->Msg));
    wsprintf(buf, 
        "MIME-Version:1.0\r\nContent-Type:text/plain; charset=gb2312\r\n"
        "Content-Transfer-Encoding:base64\r\nContent-Language:zh-cn\r\n"
        "TO: %s\r\nFROM: %s\r\nSUBJECT: %s\r\n\r\n%s\r\n.",
        pInfo->To, pInfo->From, pInfo->Subject,    szContent);

    if(Talk(sockid, "354", buf))
        goto STOP;
    strcpy(buf, "QUIT\r\n");
    if(!Talk(sockid, "250", buf))
        goto STOP;
    strcpy(buf, "");
    if(!Talk(sockid, "221", buf))
        goto STOP;
    else
    {
        closesocket(sockid);
        WSACleanup();
        return TRUE;
    }
STOP:
    closesocket(sockid);
    WSACleanup();
    return FALSE;
}
// 使用范例: 
SMTPINFO info;
strcpy(info.Server,"smtp.***.com");
info.Port = 25;
strcpy(info.UserName,"XXXXX@***.com");
strcpy(info.Password,"*****");
strcpy(info.From, "XXXXX@***.com");
strcpy(info.To, "YYYYY@YYY.com");
strcpy(info.Subject, "邮件标题");
strcpy(info.Msg, "邮件内容。");
SendMail(&info);

（5）以 Post 形式发送 HTTP 请求。如果使用 C# 则可以使用 HttpRequest。由于是测试版本，以下代码在读取服务器响应时假设服务器的响应是短文本，因此没有判断服务器的响应是否已全部读取，并不是非常完善。在实际应用中应完善后使用。

#include <Wininet.h>
BOOL SendHttpPost()
{
    HINTERNET hInternet = InternetOpen(_T("HttpPostTest"),
        INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
    if(hInternet == NULL)
        return FALSE;
    HINTERNET hConnect = InternetConnect(hInternet,
        _T("www.xxx.com"),
        INTERNET_DEFAULT_HTTP_PORT,
        NULL, //user
        NULL, //password
        INTERNET_SERVICE_HTTP, 0, 0);
    if(hConnect == NULL)
    {
        InternetCloseHandle(hInternet);
        return FALSE;
    }
    LPCTSTR szTypes[] = { _T("*/*"), NULL };
    TCHAR szData[1024], szResponse[1024];
    TCHAR szContent[1024], szTemp[128];
    //全英文的ascii字符集是UTF-8的子集，所以下面的字符串也可以看着是 UTF-8 编码的。
    _tcscpy(szContent, _T("user=xxx&password=xxx"));
    DWORD dwBytesAvailable = 0, dwBytesRead = 0; 
    HINTERNET hRequest = HttpOpenRequest(hConnect,
        _T("POST"),
        _T("/xxx/xxx.aspx"),
        NULL, //version: "HTTP/1.1"
        _T("http://www.xxx.com/xxx/xxx.aspx"), //referer
        szTypes, //types
        INTERNET_FLAG_HYPERLINK | INTERNET_FLAG_RELOAD, 0);
    if(hRequest == NULL)
    {
        InternetCloseHandle(hConnect);
        InternetCloseHandle(hInternet);
        return FALSE;
    }
    BOOL bSuccess;
    
    TCHAR headers[512];
    _stprintf(headers, _T("Content-Length: %ld\r\n"), _tcslen(szContent));
    _tcscat(headers, 
        _T("Content-Type: application/x-www-form-urlencoded\r\n")
        _T("xxx: yyy\r\n")
        );
    bSuccess = HttpSendRequest(hRequest,
        headers, //additional header
        _tcslen(headers), //headersLength
        szContent,
        _tcslen(szContent));
    TCHAR szBuffer[1024];
    DWORD bufLen = sizeof(szBuffer);
    DWORD dwIndex = 0;
    if(bSuccess)
    {
        //查询服务器返回的headers信息，内含传输内容使用的编码。
        HttpQueryInfo(hRequest, HTTP_QUERY_RAW_HEADERS_CRLF, 
            szBuffer,
            &bufLen, &dwIndex);
        InternetQueryDataAvailable(hRequest, &dwBytesAvailable, 0, 0);
        bSuccess = InternetReadFile(hRequest, szResponse, sizeof(szResponse), &dwBytesRead);
        int count = MultiByteToWideChar(CP_UTF8, 0, szResponse, dwBytesRead, szDataUnicode, sizeof(szDataUnicode)/sizeof(szDataUnicode[0]));
        count = WideCharToMultiByte(CP_ACP, 0, szDataUnicode, count, szData, sizeof(szData)/sizeof(szData[0]), NULL, NULL);
        szData[count] = '\0';
    }
    InternetCloseHandle(hRequest);
    InternetCloseHandle(hConnect);
    InternetCloseHandle(hInternet);
    return bSuccess;
}

 

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