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

你可以使用embeddedRest库。它是一个轻量级的头文件库。所以很容易将它包含到你的项目中，它不需要编译，因为里面没有。cpp文件。

从自述文件中请求示例。Md from repo:

#include "UrlRequest.hpp"

//...

UrlRequest request;
request.host("api.vk.com");
const auto countryId = 1;
const auto count = 1000;
request.uri("/method/database.getCities",{
    { "lang", "ru" },
    { "country_id", countryId },
    { "count", count },
    { "need_all", "1" },
});
request.addHeader("Content-Type: application/json");
auto response = std::move(request.perform());
if (response.statusCode() == 200) {
  cout << "status code = " << response.statusCode() << ", body = *" << response.body() << "*" << endl;
}else{
  cout << "status code = " << response.statusCode() << ", description = " << response.statusDescription() << endl;
}

如果您正在寻找在多个平台(Linux, Windows和Mac)支持的c++中的HTTP客户端库，以使用Restful web服务。您可以有以下选项。

QT网络库-允许应用程序发送网络请求并接收回复 c++ REST SDK -一个新兴的支持PPL的第三方HTTP库 Libcurl -它可能是本地世界中使用最多的http库之一。

一般来说，我会推荐一些跨平台的工具，比如cURL、POCO或Qt。：

#include <atlbase.h>
#include <msxml6.h>
#include <comutil.h> // _bstr_t

HRESULT hr;
CComPtr<IXMLHTTPRequest> request;

hr = request.CoCreateInstance(CLSID_XMLHTTP60);
hr = request->open(
    _bstr_t("GET"),
    _bstr_t("https://www.google.com/images/srpr/logo11w.png"),
    _variant_t(VARIANT_FALSE),
    _variant_t(),
    _variant_t());
hr = request->send(_variant_t());

// get status - 200 if succuss
long status;
hr = request->get_status(&status);

// load image data (if url points to an image)
VARIANT responseVariant;
hr = request->get_responseStream(&responseVariant);
IStream* stream = (IStream*)responseVariant.punkVal;
CImage *image = new CImage();
image->Load(stream);
stream->Release();

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

Windows代码:

#include <string.h>
#include <winsock2.h>
#include <windows.h>
#include <iostream>
#include <vector>
#include <locale>
#include <sstream>
using namespace std;
#pragma comment(lib,"ws2_32.lib")




int main( void ){

WSADATA wsaData;
SOCKET Socket;
SOCKADDR_IN SockAddr;
int lineCount=0;
int rowCount=0;
struct hostent *host;
locale local;
char buffer[10000];
int i = 0 ;
int nDataLength;
string website_HTML;

// website url
string url = "www.google.com";

//HTTP GET
string get_http = "GET / HTTP/1.1\r\nHost: " + url + "\r\nConnection: close\r\n\r\n";


    if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0){
        cout << "WSAStartup failed.\n";
        system("pause");
        //return 1;
    }

    Socket=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
    host = gethostbyname(url.c_str());

    SockAddr.sin_port=htons(80);
    SockAddr.sin_family=AF_INET;
    SockAddr.sin_addr.s_addr = *((unsigned long*)host->h_addr);

    if(connect(Socket,(SOCKADDR*)(&SockAddr),sizeof(SockAddr)) != 0){
        cout << "Could not connect";
        system("pause");
        //return 1;
    }

    // send GET / HTTP
    send(Socket,get_http.c_str(), strlen(get_http.c_str()),0 );

    // recieve html
    while ((nDataLength = recv(Socket,buffer,10000,0)) > 0){        
        int i = 0;
        while (buffer[i] >= 32 || buffer[i] == '\n' || buffer[i] == '\r'){

            website_HTML+=buffer[i];
            i += 1;
        }               
    }

    closesocket(Socket);
    WSACleanup();

    // Display HTML source 
    cout<<website_HTML;

    // pause
    cout<<"\n\nPress ANY key to close.\n\n";
    cin.ignore(); cin.get(); 


 return 0;
}

下面是一个更好的实现:

#include <windows.h>
#include <string>
#include <stdio.h>

using std::string;

#pragma comment(lib,"ws2_32.lib")


HINSTANCE hInst;
WSADATA wsaData;
void mParseUrl(char *mUrl, string &serverName, string &filepath, string &filename);
SOCKET connectToServer(char *szServerName, WORD portNum);
int getHeaderLength(char *content);
char *readUrl2(char *szUrl, long &bytesReturnedOut, char **headerOut);


int main()
{
    const int bufLen = 1024;
    char *szUrl = "http://stackoverflow.com";
    long fileSize;
    char *memBuffer, *headerBuffer;
    FILE *fp;

    memBuffer = headerBuffer = NULL;

    if ( WSAStartup(0x101, &wsaData) != 0)
        return -1;


    memBuffer = readUrl2(szUrl, fileSize, &headerBuffer);
    printf("returned from readUrl\n");
    printf("data returned:\n%s", memBuffer);
    if (fileSize != 0)
    {
        printf("Got some data\n");
        fp = fopen("downloaded.file", "wb");
        fwrite(memBuffer, 1, fileSize, fp);
        fclose(fp);
         delete(memBuffer);
        delete(headerBuffer);
    }

    WSACleanup();
    return 0;
}


void mParseUrl(char *mUrl, string &serverName, string &filepath, string &filename)
{
    string::size_type n;
    string url = mUrl;

    if (url.substr(0,7) == "http://")
        url.erase(0,7);

    if (url.substr(0,8) == "https://")
        url.erase(0,8);

    n = url.find('/');
    if (n != string::npos)
    {
        serverName = url.substr(0,n);
        filepath = url.substr(n);
        n = filepath.rfind('/');
        filename = filepath.substr(n+1);
    }

    else
    {
        serverName = url;
        filepath = "/";
        filename = "";
    }
}

SOCKET connectToServer(char *szServerName, WORD portNum)
{
    struct hostent *hp;
    unsigned int addr;
    struct sockaddr_in server;
    SOCKET conn;

    conn = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (conn == INVALID_SOCKET)
        return NULL;

    if(inet_addr(szServerName)==INADDR_NONE)
    {
        hp=gethostbyname(szServerName);
    }
    else
    {
        addr=inet_addr(szServerName);
        hp=gethostbyaddr((char*)&addr,sizeof(addr),AF_INET);
    }

    if(hp==NULL)
    {
        closesocket(conn);
        return NULL;
    }

    server.sin_addr.s_addr=*((unsigned long*)hp->h_addr);
    server.sin_family=AF_INET;
    server.sin_port=htons(portNum);
    if(connect(conn,(struct sockaddr*)&server,sizeof(server)))
    {
        closesocket(conn);
        return NULL;
    }
    return conn;
}

int getHeaderLength(char *content)
{
    const char *srchStr1 = "\r\n\r\n", *srchStr2 = "\n\r\n\r";
    char *findPos;
    int ofset = -1;

    findPos = strstr(content, srchStr1);
    if (findPos != NULL)
    {
        ofset = findPos - content;
        ofset += strlen(srchStr1);
    }

    else
    {
        findPos = strstr(content, srchStr2);
        if (findPos != NULL)
        {
            ofset = findPos - content;
            ofset += strlen(srchStr2);
        }
    }
    return ofset;
}

char *readUrl2(char *szUrl, long &bytesReturnedOut, char **headerOut)
{
    const int bufSize = 512;
    char readBuffer[bufSize], sendBuffer[bufSize], tmpBuffer[bufSize];
    char *tmpResult=NULL, *result;
    SOCKET conn;
    string server, filepath, filename;
    long totalBytesRead, thisReadSize, headerLen;

    mParseUrl(szUrl, server, filepath, filename);

    ///////////// step 1, connect //////////////////////
    conn = connectToServer((char*)server.c_str(), 80);

    ///////////// step 2, send GET request /////////////
    sprintf(tmpBuffer, "GET %s HTTP/1.0", filepath.c_str());
    strcpy(sendBuffer, tmpBuffer);
    strcat(sendBuffer, "\r\n");
    sprintf(tmpBuffer, "Host: %s", server.c_str());
    strcat(sendBuffer, tmpBuffer);
    strcat(sendBuffer, "\r\n");
    strcat(sendBuffer, "\r\n");
    send(conn, sendBuffer, strlen(sendBuffer), 0);

//    SetWindowText(edit3Hwnd, sendBuffer);
    printf("Buffer being sent:\n%s", sendBuffer);

    ///////////// step 3 - get received bytes ////////////////
    // Receive until the peer closes the connection
    totalBytesRead = 0;
    while(1)
    {
        memset(readBuffer, 0, bufSize);
        thisReadSize = recv (conn, readBuffer, bufSize, 0);

        if ( thisReadSize <= 0 )
            break;

        tmpResult = (char*)realloc(tmpResult, thisReadSize+totalBytesRead);

        memcpy(tmpResult+totalBytesRead, readBuffer, thisReadSize);
        totalBytesRead += thisReadSize;
    }

    headerLen = getHeaderLength(tmpResult);
    long contenLen = totalBytesRead-headerLen;
    result = new char[contenLen+1];
    memcpy(result, tmpResult+headerLen, contenLen);
    result[contenLen] = 0x0;
    char *myTmp;

    myTmp = new char[headerLen+1];
    strncpy(myTmp, tmpResult, headerLen);
    myTmp[headerLen] = NULL;
    delete(tmpResult);
    *headerOut = myTmp;

    bytesReturnedOut = contenLen;
    closesocket(conn);
    return(result);
}