Unfortunately, standard C++ library doesn’t provide tools for working with HTTP. Therefore, when we want to run a REST service, parse a webpage or write a simple bot or web crawler, we always wonder which library is better to use. Sometimes a project already uses some framework (or even several). But how do we create an HTTP request using available facilities? Not to get confused each time performing such tasks, I decided to make a cheat sheet with examples of HTTP requests in C++ using different libraries. I guess Kukuruku is the best place for keeping such cheat sheets.

We’re going to take a look at the following libraries:

WinInet

WinHttp

Casablanca

Qt

POCO

wxWidgets

Boost.Asio

libcurl

neon

.NET (С++/CLI)

IXMLHTTPRequest

HappyHttp

cpp-netlib

WinInet

Website: http://msdn.microsoft.com/en-us/library/windows/desktop/aa385483(v=vs.85).aspx Platform: Windows 95 and later

#include <tchar.h> #include <wininet.h> /// .... HINTERNET hIntSession = ::InternetOpen(_T("MyApp"), INTERNET_OPEN_TYPE_DIRECT, NULL, NULL, 0); HINTERNET hHttpSession = InternetConnect(hIntSession, _T("api.twitter.com"), 80, 0, 0, INTERNET_SERVICE_HTTP, 0, NULL); HINTERNET hHttpRequest = HttpOpenRequest( hHttpSession, _T("GET"), _T("1/statuses/user_timeline.xml?screen_name=twitterapi"), 0, 0, 0, INTERNET_FLAG_RELOAD, 0); TCHAR* szHeaders = _T("Content-Type: text/html

MySpecialHeder: whatever"); CHAR szReq[1024] = ""; if( !HttpSendRequest(hHttpRequest, szHeaders, _tcslen(szHeaders), szReq, strlen(szReq))) { DWORD dwErr = GetLastError(); /// handle error } CHAR szBuffer[1025]; DWORD dwRead=0; while(::InternetReadFile(hHttpRequest, szBuffer, sizeof(szBuffer)-1, &dwRead) && dwRead) { szBuffer[dwRead] = 0; OutputDebugStringA(szBuffer); dwRead=0; } ::InternetCloseHandle(hHttpRequest); ::InternetCloseHandle(hHttpSession); ::InternetCloseHandle(hIntSession);

WinHttp

Website: http://msdn.microsoft.com/en-us/library/windows/desktop/aa382925(v=vs.85).aspx Platform: Windows 2000 and later

DWORD dwSize = 0; DWORD dwDownloaded = 0; LPSTR pszOutBuffer; BOOL bResults = FALSE; HINTERNET hSession = NULL, hConnect = NULL, hRequest = NULL; // Use WinHttpOpen to obtain a session handle. hSession = WinHttpOpen( L"WinHTTP Example/1.0", WINHTTP_ACCESS_TYPE_DEFAULT_PROXY, WINHTTP_NO_PROXY_NAME, WINHTTP_NO_PROXY_BYPASS, 0 ); // Specify an HTTP server. if( hSession ) hConnect = WinHttpConnect( hSession, L"www.microsoft.com", INTERNET_DEFAULT_HTTPS_PORT, 0 ); // Create an HTTP request handle. if( hConnect ) hRequest = WinHttpOpenRequest( hConnect, L"GET", NULL, NULL, WINHTTP_NO_REFERER, WINHTTP_DEFAULT_ACCEPT_TYPES, WINHTTP_FLAG_SECURE ); // Send a request. if( hRequest ) bResults = WinHttpSendRequest( hRequest, WINHTTP_NO_ADDITIONAL_HEADERS, 0, WINHTTP_NO_REQUEST_DATA, 0, 0, 0 ); // End the request. if( bResults ) bResults = WinHttpReceiveResponse( hRequest, NULL ); // Keep checking for data until there is nothing left. if( bResults ) { do { // Check for available data. dwSize = 0; if( !WinHttpQueryDataAvailable( hRequest, &dwSize ) ) printf( "Error %u in WinHttpQueryDataAvailable.

", GetLastError( ) ); // Allocate space for the buffer. pszOutBuffer = new char[dwSize+1]; if( !pszOutBuffer ) { printf( "Out of memory

" ); dwSize=0; } else { // Read the data. ZeroMemory( pszOutBuffer, dwSize+1 ); if( !WinHttpReadData( hRequest, (LPVOID)pszOutBuffer, dwSize, &dwDownloaded ) ) printf( "Error %u in WinHttpReadData.

", GetLastError( ) ); else printf( "%s", pszOutBuffer ); // Free the memory allocated to the buffer. delete [] pszOutBuffer; } } while( dwSize > 0 ); } // Report any errors. if( !bResults ) printf( "Error %d has occurred.

", GetLastError( ) ); // Close any open handles. if( hRequest ) WinHttpCloseHandle( hRequest ); if( hConnect ) WinHttpCloseHandle( hConnect ); if( hSession ) WinHttpCloseHandle( hSession );

Casablanca

Website: https://casablanca.codeplex.com Platform: all

http_client client(L"http://www.myhttpserver.com"); http_request request(methods::GET); client.request(request).then([](http_response response) { // Perform actions here to inspect the HTTP response... if(response.status_code() == status_codes::OK) { } });

Qt

Website: http://qt-project.org Platform: all

#include "handler.h" Handler::Handler(QObject *parent) :QObject(parent) { http = new QHttp(this); connect(http, SIGNAL(stateChanged(int)), this, SLOT(stateChanged(int))); connect(http, SIGNAL(responseHeaderReceived(QHttpResponseHeader)), this, SLOT(responseHeaderReceived(QHttpResponseHeader))); connect(http, SIGNAL(requestFinished(int,bool)), this, SLOT(requestFinished(int,bool))); } void Handler::doHttp() { http->setHost("google.com"); http->get("/"); } void Handler::stateChanged(int state) { switch(state) { case 0: qDebug() << "Unconnected"; break; case 1: qDebug() << "Host Lookup"; break; case 2: qDebug() << "Connecting"; break; case 3: qDebug() << "Sending"; break; case 4: qDebug() << "Reading"; break; case 5: qDebug() << "Connect"; break; case 6: qDebug() << "Closing"; break; } } void Handler::responseHeaderReceived(const QHttpResponseHeader &resp) { qDebug() << "Size : " << resp.contentLength(); qDebug() << "Type : " << resp.contentType(); qDebug() << "Status Code : " << resp.statusCode(); } void Handler::requestFinished(int id, bool error) { qDebug() << "Request Id : " << id; if(error) { qDebug() << "Error"; } else { qDebug() << http->readAll(); } }

Example use for Qt 5.x

void Downloader::doDownload() { manager = new QNetworkAccessManager(this); connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*))); manager->get(QNetworkRequest(QUrl("http://google.com"))); } void Downloader::replyFinished (QNetworkReply *reply) { if(reply->error() != QNetworkReply::NoError) { qDebug() << "ERROR!"; qDebug() << reply->errorString(); } else { qDebug() << reply->header(QNetworkRequest::ContentTypeHeader).toString(); qDebug() << reply->header(QNetworkRequest::LastModifiedHeader).toDateTime().toString(); qDebug() << reply->header(QNetworkRequest::ContentLengthHeader).toULongLong(); qDebug() << reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt(); qDebug() << reply->attribute(QNetworkRequest::HttpReasonPhraseAttribute).toString(); QFile file("C:/Qt/Dummy/downloaded.txt"); if(file.open(QFile::Append)) { file.write(reply->readAll()); } } reply->deleteLater(); }

POCO

Website: http://pocoproject.org Platform: all

#include <Poco/Net/HTTPClientSession.h> #include <Poco/Net/HTTPRequest.h> #include <Poco/Net/HTTPResponse.h> #include <Poco/StreamCopier.h> #include <Poco/Path.h> #include <Poco/URI.h> #include <Poco/Exception.h> #include <iostream> #include <string> using namespace Poco::Net; using namespace Poco; using namespace std; int main(int argc, char **argv) { if (argc != 2) { cout << "Usage: " << argv[0] << " <uri>" << endl; cout << " fetches the resource identified by <uri> and print it" << endl; return -1; } try { // prepare session URI uri(argv[1]); HTTPClientSession session(uri.getHost(), uri.getPort()); // prepare path string path(uri.getPathAndQuery()); if (path.empty()) path = "/"; // send request HTTPRequest req(HTTPRequest::HTTP_GET, path, HTTPMessage::HTTP_1_1); session.sendRequest(req); // get response HTTPResponse res; cout << res.getStatus() << " " << res.getReason() << endl; // print response istream &is = session.receiveResponse(res); StreamCopier::copyStream(is, cout); } catch (Exception &ex) { cerr << ex.displayText() << endl; return -1; } return 0; }

wxWidgets

Website: http://www.wxwidgets.org Platform: all

#include <wx/sstream.h> #include <wx/protocol/http.h> wxHTTP get; get.SetHeader(_T("Content-type"), _T("text/html; charset=utf-8")); get.SetTimeout(10); // 10 seconds of timeout instead of 10 minutes ... // this will wait until the user connects to the internet. It is important in case of dialup (or ADSL) connections while (!get.Connect(_T("www.google.com"))) // only the server, no pages here yet ... wxSleep(5); wxApp::IsMainLoopRunning(); // should return true // use _T("/") for index.html, index.php, default.asp, etc. wxInputStream *httpStream = get.GetInputStream(_T("/intl/en/about.html")); // wxLogVerbose( wxString(_T(" GetInputStream: ")) << get.GetResponse() << _T("-") << ((resStream)? _T("OK ") : _T("FAILURE ")) << get.GetError() ); if (get.GetError() == wxPROTO_NOERR) { wxString res; wxStringOutputStream out_stream(&res); httpStream->Read(out_stream); wxMessageBox(res); // wxLogVerbose( wxString(_T(" returned document length: ")) << res.Length() ); } else { wxMessageBox(_T("Unable to connect!")); } wxDELETE(httpStream); get.Close();

Boost.Asio

Website: http://www.boost.org/doc/libs/1_55_0/doc/html/boost_asio.html Platform: all

#include <iostream> #include <istream> #include <ostream> #include <string> #include <boost/asio.hpp> using boost::asio::ip::tcp; int main(int argc, char* argv[]) { try { if (argc != 3) { std::cout << "Usage: sync_client <server> <path>

"; std::cout << "Example:

"; std::cout << " sync_client www.boost.org /LICENSE_1_0.txt

"; return 1; } boost::asio::io_service io_service; // Get a list of endpoints corresponding to the server name. tcp::resolver resolver(io_service); tcp::resolver::query query(argv[1], "http"); tcp::resolver::iterator endpoint_iterator = resolver.resolve(query); // Try each endpoint until we successfully establish a connection. tcp::socket socket(io_service); boost::asio::connect(socket, endpoint_iterator); // Form the request. We specify the "Connection: close" header so that the // server will close the socket after transmitting the response. This will // allow us to treat all data up until the EOF as the content. boost::asio::streambuf request; std::ostream request_stream(&request); request_stream << "GET " << argv[2] << " HTTP/1.0\r

"; request_stream << "Host: " << argv[1] << "\r

"; request_stream << "Accept: */*\r

"; request_stream << "Connection: close\r

\r

"; // Send the request. boost::asio::write(socket, request); // Read the response status line. The response streambuf will automatically // grow to accommodate the entire line. The growth may be limited by passing // a maximum size to the streambuf constructor. boost::asio::streambuf response; boost::asio::read_until(socket, response, "\r

"); // Check that response is OK. std::istream response_stream(&response); std::string http_version; response_stream >> http_version; unsigned int status_code; response_stream >> status_code; std::string status_message; std::getline(response_stream, status_message); if (!response_stream || http_version.substr(0, 5) != "HTTP/") { std::cout << "Invalid response

"; return 1; } if (status_code != 200) { std::cout << "Response returned with status code " << status_code << "

"; return 1; } // Read the response headers, which are terminated by a blank line. boost::asio::read_until(socket, response, "\r

\r

"); // Process the response headers. std::string header; while (std::getline(response_stream, header) && header != "\r") std::cout << header << "

"; std::cout << "

"; // Write whatever content we already have to output. if (response.size() > 0) std::cout << &response; // Read until EOF, writing data to output as we go. boost::system::error_code error; while (boost::asio::read(socket, response, boost::asio::transfer_at_least(1), error)) std::cout << &response; if (error != boost::asio::error::eof) throw boost::system::system_error(error); } catch (std::exception& e) { std::cout << "Exception: " << e.what() << "

"; } return 0; }

libcurl

Website: http://curl.haxx.se/libcurl Platform: all

#include <stdio.h> #include <curl/curl.h> int main(void) { CURL *curl; CURLcode res; curl = curl_easy_init(); if(curl) { curl_easy_setopt(curl, CURLOPT_URL, "http://example.com"); /* example.com is redirected, so we tell libcurl to follow redirection */ curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L); /* Perform the request, res will get the return code */ res = curl_easy_perform(curl); /* Check for errors */ if(res != CURLE_OK) fprintf(stderr, "curl_easy_perform() failed: %s

", curl_easy_strerror(res)); /* always cleanup */ curl_easy_cleanup(curl); } return 0; }

neon

Website: http://www.webdav.org/neon Platform: all

#include <ne_session.h> #include <ne_request.h> #include <ne_utils.h> #include <ne_uri.h> int httpResponseReader(void *userdata, const char *buf, size_t len) { string *str = (string *)userdata; str->append(buf, len); return 0; } int do_get(string host) { ne_session *sess; ne_request *req; string response; ne_sock_init(); sess = ne_session_create("http", host.c_str(), 80); ne_set_useragent(sess, "MyAgent/1.0"); req = ne_request_create(sess, "GET", "/SomeURL/method?with=parameter&value=data"); // if accepting only 2xx codes, use "ne_accept_2xx" ne_add_response_body_reader(req, ne_accept_always, httpResponseReader, &response); int result = ne_request_dispatch(req); int status = ne_get_status(req)->code; ne_request_destroy(req); string errorMessage = ne_get_error(sess); ne_session_destroy(sess); printf("result %d, status %d

", result, status); cout << response << "

"; switch (result) { case NE_OK: break; case NE_CONNECT: throw ConnectionError(errorMessage); case NE_TIMEOUT: throw TimeOutError(errorMessage); case NE_AUTH: throw AuthenticationError(errorMessage); default: throw AnotherWebError(errorMessage); } return 0; }

.NET

Website: http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.aspx Platform: Windows XP and later

#using <System.dll> using namespace System; using namespace System::Net; using namespace System::Text; using namespace System::IO; // Specify the URL to receive the request. int main() { array<String^>^args = Environment::GetCommandLineArgs(); HttpWebRequest^ request = dynamic_cast<HttpWebRequest^>(WebRequest::Create( args[ 1 ] )); // Set some reasonable limits on resources used by this request request->MaximumAutomaticRedirections = 4; request->MaximumResponseHeadersLength = 4; // Set credentials to use for this request. request->Credentials = CredentialCache::DefaultCredentials; HttpWebResponse^ response = dynamic_cast<HttpWebResponse^>(request->GetResponse()); Console::WriteLine( "Content length is {0}", response->ContentLength ); Console::WriteLine( "Content type is {0}", response->ContentType ); // Get the stream associated with the response. Stream^ receiveStream = response->GetResponseStream(); // Pipes the stream to a higher level stream reader with the required encoding format. StreamReader^ readStream = gcnew StreamReader( receiveStream,Encoding::UTF8 ); Console::WriteLine( "Response stream received." ); Console::WriteLine( readStream->ReadToEnd() ); response->Close(); readStream->Close(); }

IXMLHTTPRequest

Website: http://msdn.microsoft.com/en-us/library/ms759148(v=vs.85).aspx Platform: Windows XP and later

#include <atlbase.h> #include <msxml6.h> 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();

HappyHttp

Website: http://scumways.com/happyhttp/happyhttp.html Platform: all

static int count=0; // invoked when response headers have been received void OnBegin( const happyhttp::Response* r, void* userdata ) { printf( "BEGIN (%d %s)

", r->getstatus(), r->getreason() ); count = 0; } // invoked to process response body data (may be called multiple times) void OnData( const happyhttp::Response* r, void* userdata, const unsigned char* data, int n ) { fwrite( data,1,n, stdout ); count += n; } // invoked when response is complete void OnComplete( const happyhttp::Response* r, void* userdata ) { printf( "COMPLETE (%d bytes)

", count ); } void TestGET() { happyhttp::Connection conn( "www.scumways.com", 80 ); conn.setcallbacks( OnBegin, OnData, OnComplete, 0 ); conn.request( "GET", "/happyhttp/test.php" ); while( conn.outstanding() ) conn.pump(); }

cpp-netlib

Website: http://cpp-netlib.org Platform: all

using namespace boost::network; using namespace boost::network::http; client::request request_("http://127.0.0.1:8000/"); request_ << header("Connection", "close"); client client_; client::response response_ = client_.get(request_); std::string body_ = body(response_);

It’s High Time to Find Out the Perfect One!

If you want to use the trusted classics – use libcurl. If you’re writing an application with a visual interface – use Qt. For those writing in С++11, Casablanca is the best choice. If you’re writing under .NET, then you should use what’s available in the platform’s standard. But if you’re writing something with no interface, and besides an HTTP client you also want to have various handy tools, use Boost or POCO.