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
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。
其他回答
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// "getaddrinfo" function which outdated "gethostbyname".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
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…
MS的CppRest SDK是我刚刚发现的,大约半小时后,我的第一个简单的web服务调用工作。相比之下,在这里提到的其他地方,我甚至无法安装任何东西,我不得不说,这是相当令人印象深刻的
https://github.com/microsoft/cpprestsdk
向下滚动,点击文档,然后点击入门教程,你将有一个简单的应用程序运行在任何时间。
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
你可能想要检查c++ REST SDK(代号“Casablanca”)。http://msdn.microsoft.com/en-us/library/jj950081.aspx
使用c++ REST SDK,您可以更轻松地从c++应用程序连接到HTTP服务器。
使用的例子:
#include <iostream>
#include <cpprest/http_client.h>
using namespace web::http; // Common HTTP functionality
using namespace web::http::client; // HTTP client features
int main(int argc, char** argv) {
http_client client("http://httpbin.org/");
http_response response;
// ordinary `get` request
response = client.request(methods::GET, "/get").get();
std::cout << response.extract_string().get() << "\n";
// working with json
response = client.request(methods::GET, "/get").get();
std::cout << "url: " << response.extract_json().get()[U("url")] << "\n";
}
c++ REST SDK是微软的一个项目,用于使用现代异步c++ API设计的本地代码进行基于云的客户端-服务器通信。