A Cheat Sheet for HTTP Libraries in C++

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 
    #include   

    /// ....

    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\nMySpecialHeder: 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.\n",
                GetLastError( ) );

      // Allocate space for the buffer.
      pszOutBuffer = new char[dwSize+1];
      if( !pszOutBuffer )
      {
        printf( "Out of memory\n" );
        dwSize=0;
      }
      else
      {
        // Read the data.
        ZeroMemory( pszOutBuffer, dwSize+1 );

        if( !WinHttpReadData( hRequest, (LPVOID)pszOutBuffer, 
                              dwSize, &dwDownloaded ) )
          printf( "Error %u in WinHttpReadData.\n", 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.\n", 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() 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() errorString();
    }
    else
    {
        qDebug() header(QNetworkRequest::ContentTypeHeader).toString();
        qDebug() header(QNetworkRequest::LastModifiedHeader).toDateTime().toString();
        qDebug() header(QNetworkRequest::ContentLengthHeader).toULongLong();
        qDebug() attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
        qDebug() 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 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace Poco::Net;
using namespace Poco;
using namespace std;

int main(int argc, char **argv)
{
  if (argc != 2)
  {
    cout "  and print it" 

wxWidgets

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

#include 
#include 
 
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: ")) Read(out_stream);
 
    wxMessageBox(res);
    // wxLogVerbose( wxString(_T(" returned document length: ")) 

Boost.Asio

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

#include 
#include 
#include 
#include 
#include 

using boost::asio::ip::tcp;

int main(int argc, char* argv[])
{
  try
  {
    if (argc != 3)
    {
      std::cout  \n";
      std::cout > 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  0)
      std::cout 

libcurl

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

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

neon

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

#include 
#include 
#include 
#include 

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\n", result, status);
    cout 

.NET

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

#using 

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^args = Environment::GetCommandLineArgs();
   HttpWebRequest^ request = dynamic_cast(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(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 
#include 

HRESULT hr;
CComPtr 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)\n", 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)\n", 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_ 

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.