有什么方法可以简单地用c++发出HTTP请求吗?具体来说,我想下载一个页面(一个API)的内容,并检查内容,看看它是否包含1或0。是否也可以将内容下载到字符串中?
当前回答
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// "getaddrinfo" function which outdated "gethostbyname".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
其他回答
2020年更新:我有一个新的答案来取代这个已经存在了8年的答案:https://stackoverflow.com/a/61177330/278976
在Linux上,我尝试了cppp -netlib、libcurl、curlpp、urdl、boost::asio,并考虑过Qt(但基于许可证拒绝了它)。所有这些都不是不完整的,有草率的界面,有糟糕的文档,没有维护或不支持https。
然后,在https://stackoverflow.com/a/1012577/278976的建议下,我尝试了POCO。哇,我真希望几年前就能看到。下面是一个使用POCO进行HTTP GET请求的示例:
https://stackoverflow.com/a/26026828/2817595
POCO是免费的、开源的(boost许可证)。不,我和这家公司没有任何关系;我真的很喜欢他们的界面。干得好,伙计们(和姑娘们)。
https://pocoproject.org/download.html
希望这能帮助到某人…我花了三天时间把所有这些库都试了一遍。
现在正在开发一种更新的、不太成熟的卷曲包装器,称为c++ Requests。下面是一个简单的GET请求:
#include <iostream>
#include <cpr.h>
int main(int argc, char** argv) {
auto response = cpr::Get(cpr::Url{"http://httpbin.org/get"});
std::cout << response.text << std::endl;
}
它支持各种各样的HTTP动词和curl选项。这里有更多的使用文档。
免责声明:我是这个库的维护者。
我也有同样的问题。Libcurl真的很完整。如果您需要c++库,可能会对c++包装器curlpp感兴趣。neon是另一个有趣的C库,它也支持WebDAV。
如果你使用c++, curlpp看起来很自然。源代码发行版中提供了许多示例。 要获取URL的内容,你可以这样做(从示例中提取):
// Edit : rewritten for cURLpp 0.7.3
// Note : namespace changed, was cURLpp in 0.7.2 ...
#include <curlpp/cURLpp.hpp>
#include <curlpp/Options.hpp>
// RAII cleanup
curlpp::Cleanup myCleanup;
// Send request and get a result.
// Here I use a shortcut to get it in a string stream ...
std::ostringstream os;
os << curlpp::options::Url(std::string("http://example.com"));
string asAskedInQuestion = os.str();
参见curlpp源代码分发中的示例目录,有很多更复杂的情况,以及使用curlpp的简单完整的最小情况。
我的2美分…
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。
这是我关于cURL的最小包装器,它能够以字符串的形式获取网页。例如,这对于单元测试很有用。它基本上是一个围绕C代码的RAII包装器。
在你的机器上安装libcurl libcurl-devel或等效的。
使用的例子:
CURLplusplus client;
string x = client.Get("http://google.com");
string y = client.Get("http://yahoo.com");
类的实现:
#include <curl/curl.h>
class CURLplusplus
{
private:
CURL* curl;
stringstream ss;
long http_code;
public:
CURLplusplus()
: curl(curl_easy_init())
, http_code(0)
{
}
~CURLplusplus()
{
if (curl) curl_easy_cleanup(curl);
}
std::string Get(const std::string& url)
{
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, this);
ss.str("");
http_code = 0;
res = curl_easy_perform(curl);
if (res != CURLE_OK)
{
throw std::runtime_error(curl_easy_strerror(res));
}
curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code);
return ss.str();
}
long GetHttpCode()
{
return http_code;
}
private:
static size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp)
{
return static_cast<CURLplusplus*>(userp)->Write(buffer,size,nmemb);
}
size_t Write(void *buffer, size_t size, size_t nmemb)
{
ss.write((const char*)buffer,size*nmemb);
return size*nmemb;
}
};