下面是一些无需使用任何第三方库即可工作的代码: 首先定义网关、用户、密码和需要发送到此特定服务器的任何其他参数。

#define USERNAME "user"
#define PASSWORD "your password"
#define GATEWAY "your gateway"

下面是代码本身:

HINTERNET hOpenHandle, hResourceHandle, hConnectHandle;
const TCHAR* szHeaders = _T("Content-Type:application/json; charset=utf-8\r\n");


hOpenHandle = InternetOpen(_T("HTTPS"), INTERNET_OPEN_TYPE_DIRECT, NULL, NULL, 0);
if (hOpenHandle == NULL)
{
    return false;
}


hConnectHandle = InternetConnect(hOpenHandle,
    GATEWAY,
    INTERNET_DEFAULT_HTTPS_PORT,
    NULL, NULL, INTERNET_SERVICE_HTTP,
    0, 1);

if (hConnectHandle == NULL)
{
    InternetCloseHandle(hOpenHandle);
    return false;
}


hResourceHandle = HttpOpenRequest(hConnectHandle,
    _T("POST"),
    GATEWAY,
    NULL, NULL, NULL, INTERNET_FLAG_SECURE | INTERNET_FLAG_KEEP_CONNECTION,
    1);

if (hResourceHandle == NULL)
{
    InternetCloseHandle(hOpenHandle);
    InternetCloseHandle(hConnectHandle);
    return false;
}

InternetSetOption(hResourceHandle, INTERNET_OPTION_USERNAME, (LPVOID)USERNAME, _tcslen(USERNAME));
InternetSetOption(hResourceHandle, INTERNET_OPTION_PASSWORD, (LPVOID)PASSWORD, _tcslen(PASSWORD));

std::string buf;
if (HttpSendRequest(hResourceHandle, szHeaders, 0, NULL, 0))
{
    while (true)
    {
        std::string part;
        DWORD size;
        if (!InternetQueryDataAvailable(hResourceHandle, &size, 0, 0))break;
        if (size == 0)break;
        part.resize(size);
        if (!InternetReadFile(hResourceHandle, &part[0], part.size(), &size))break;
        if (size == 0)break;
        part.resize(size);
        buf.append(part);
    }
}

if (!buf.empty())
{
    // Get data back
}

InternetCloseHandle(hResourceHandle);
InternetCloseHandle(hConnectHandle);
InternetCloseHandle(hOpenHandle);

这应该在Win32 API环境中工作。

这里有一个例子。

下面是一些(相对)简单的c++ 11代码，使用libCURL将URL的内容下载到std::vector<char>:

http_download.hh

# pragma once

#include <string>
#include <vector>

std::vector<char> download(std::string url, long* responseCode = nullptr);

http_download.cc

#include "http_download.hh"

#include <curl/curl.h>
#include <sstream>
#include <stdexcept>

using namespace std;

size_t callback(void* contents, size_t size, size_t nmemb, void* user)
{
  auto chunk = reinterpret_cast<char*>(contents);
  auto buffer = reinterpret_cast<vector<char>*>(user);

  size_t priorSize = buffer->size();
  size_t sizeIncrease = size * nmemb;

  buffer->resize(priorSize + sizeIncrease);
  std::copy(chunk, chunk + sizeIncrease, buffer->data() + priorSize);

  return sizeIncrease;
}

vector<char> download(string url, long* responseCode)
{
  vector<char> data;

  curl_global_init(CURL_GLOBAL_ALL);
  CURL* handle = curl_easy_init();
  curl_easy_setopt(handle, CURLOPT_URL, url.c_str());
  curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, callback);
  curl_easy_setopt(handle, CURLOPT_WRITEDATA, &data);
  curl_easy_setopt(handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
  CURLcode result = curl_easy_perform(handle);
  if (responseCode != nullptr)
    curl_easy_getinfo(handle, CURLINFO_RESPONSE_CODE, responseCode);
  curl_easy_cleanup(handle);
  curl_global_cleanup();

  if (result != CURLE_OK)
  {
    stringstream err;
    err << "Error downloading from URL \"" << url << "\": " << curl_easy_strerror(result);
    throw runtime_error(err.str());
  }

  return data;
}

HTTP协议非常简单，因此编写HTTP客户端非常简单。 这里有一个

https://github.com/pedro-vicente/lib_netsockets

它使用HTTP GET从web服务器检索文件，服务器和文件都是命令行参数。远程文件保存为本地副本。

声明:我是作者

检查http.cc https://github.com/pedro-vicente/lib_netsockets/blob/master/src/http.cc

int http_client_t::get(const char *path_remote_file)
{
  char buf_request[1024];

  //construct request message using class input parameters
  sprintf(buf_request, "GET %s HTTP/1.1\r\nHost: %s\r\nConnection: close\r\n\r\n", path_remote_file, m_server_ip.c_str());

  //send request, using built in tcp_client_t socket
  if (this->write_all(buf_request, (int)strlen(buf_request)) < 0)
  {
    return -1;
  }

编辑:编辑URL

对于这个答案，我参考了Software_Developer的答案。通过重新构建代码，我发现一些部分已弃用(gethostbyname())或不为操作提供错误处理(创建套接字，发送一些东西)。

下面的windows代码是用Visual Studio 2013和windows 8.1 64位以及windows 7 64位进行测试的。它将目标与www.google.com的Web服务器的IPv4 TCP连接。

#include <winsock2.h>
#include <WS2tcpip.h>
#include <windows.h>
#include <iostream>
#pragma comment(lib,"ws2_32.lib")
using namespace std;
    int main (){
    // Initialize Dependencies to the Windows Socket.
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) {
        cout << "WSAStartup failed.\n";
        system("pause");
        return -1;
    }

    // We first prepare some "hints" for the "getaddrinfo" function
    // to tell it, that we are looking for a IPv4 TCP Connection.
    struct addrinfo hints;
    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_INET;          // We are targeting IPv4
    hints.ai_protocol = IPPROTO_TCP;    // We are targeting TCP
    hints.ai_socktype = SOCK_STREAM;    // We are targeting TCP so its SOCK_STREAM

    // Aquiring of the IPv4 address of a host using the newer
    // "getaddrinfo" function which outdated "gethostbyname".
    // It will search for IPv4 addresses using the TCP-Protocol.
    struct addrinfo* targetAdressInfo = NULL;
    DWORD getAddrRes = getaddrinfo("www.google.com", NULL, &hints, &targetAdressInfo);
    if (getAddrRes != 0 || targetAdressInfo == NULL)
    {
        cout << "Could not resolve the Host Name" << endl;
        system("pause");
        WSACleanup();
        return -1;
    }

    // Create the Socket Address Informations, using IPv4
    // We dont have to take care of sin_zero, it is only used to extend the length of SOCKADDR_IN to the size of SOCKADDR
    SOCKADDR_IN sockAddr;
    sockAddr.sin_addr = ((struct sockaddr_in*) targetAdressInfo->ai_addr)->sin_addr;    // The IPv4 Address from the Address Resolution Result
    sockAddr.sin_family = AF_INET;  // IPv4
    sockAddr.sin_port = htons(80);  // HTTP Port: 80

    // We have to free the Address-Information from getaddrinfo again
    freeaddrinfo(targetAdressInfo);

    // Creation of a socket for the communication with the Web Server,
    // using IPv4 and the TCP-Protocol
    SOCKET webSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (webSocket == INVALID_SOCKET)
    {
        cout << "Creation of the Socket Failed" << endl;
        system("pause");
        WSACleanup();
        return -1;
    }

    // Establishing a connection to the web Socket
    cout << "Connecting...\n";
    if(connect(webSocket, (SOCKADDR*)&sockAddr, sizeof(sockAddr)) != 0)
    {
        cout << "Could not connect";
        system("pause");
        closesocket(webSocket);
        WSACleanup();
        return -1;
    }
    cout << "Connected.\n";

    // Sending a HTTP-GET-Request to the Web Server
    const char* httpRequest = "GET / HTTP/1.1\r\nHost: www.google.com\r\nConnection: close\r\n\r\n";
    int sentBytes = send(webSocket, httpRequest, strlen(httpRequest),0);
    if (sentBytes < strlen(httpRequest) || sentBytes == SOCKET_ERROR)
    {
        cout << "Could not send the request to the Server" << endl;
        system("pause");
        closesocket(webSocket);
        WSACleanup();
        return -1;
    }

    // Receiving and Displaying an answer from the Web Server
    char buffer[10000];
    ZeroMemory(buffer, sizeof(buffer));
    int dataLen;
    while ((dataLen = recv(webSocket, buffer, sizeof(buffer), 0) > 0))
    {
        int i = 0;
        while (buffer[i] >= 32 || buffer[i] == '\n' || buffer[i] == '\r') {
            cout << buffer[i];
            i += 1;
        }
    }

    // Cleaning up Windows Socket Dependencies
    closesocket(webSocket);
    WSACleanup();

    system("pause");
    return 0;
}

引用:

弃用gethostbyname

socket()的返回值

send()的返回值

C和c++没有用于HTTP甚至套接字连接的标准库。多年来，一些便携式图书馆已经被开发出来。正如其他人所说，使用最广泛的是libcurl。

下面是libcurl的替代品列表(来自libcurl的网站)。

另外，对于Linux，这是一个简单的HTTP客户机。您可以实现自己的简单HTTP GET客户端，但如果涉及到身份验证或重定向，或者需要在代理后工作，则这将不起作用。对于这些情况，您需要像libcurl这样成熟的库。

对于使用libcurl的源代码，这是最接近您想要的(libcurl有许多示例)。看看主要功能。成功连接后，html内容将被复制到缓冲区。只需用自己的函数替换parseHtml即可。

注意，这并不需要libcurl, Windows.h，或WinSock!没有编译库，没有项目配置，等等。我有这段代码在Windows 10上的Visual Studio 2017 c++中工作:

#pragma comment(lib, "urlmon.lib")

#include <urlmon.h>
#include <sstream>

using namespace std;

...

IStream* stream;
//Also works with https URL's - unsure about the extent of SSL support though.
HRESULT result = URLOpenBlockingStream(0, "http://google.com", &stream, 0, 0);
if (result != 0)
{
    return 1;
}
char buffer[100];
unsigned long bytesRead;
stringstream ss;
stream->Read(buffer, 100, &bytesRead);
while (bytesRead > 0U)
{
    ss.write(buffer, (long long)bytesRead);
    stream->Read(buffer, 100, &bytesRead);
}
stream->Release();
string resultString = ss.str();

我只是想出了如何做到这一点，因为我想要一个简单的API访问脚本，像libcurl这样的库给我带来了各种各样的问题(即使我遵循了说明……)，而WinSock只是太低级和复杂了。

我不太确定所有的IStream读取代码(特别是while条件-请随意纠正/改进)，但嘿，它工作，麻烦!(这对我来说是有意义的，因为我使用了一个阻塞(同步)调用，这是很好的，bytesRead将始终是> 0U，直到流(ISequentialStream?)完成读取，但谁知道呢。)

请参见:URL名称和异步可插协议参考