Hi,

I am using curl to connect to an online quote server in a C++ (VC++ 6)
Windows application. Once the http connection is established, the server
keeps sending data back. The connection code runs in its own thread and I
use a callback to receive the data - responseCallback which is a static
member of CSession.

What is the "clean" way of disconnecting from the server during this lengthy
operation, if for example I need to restart the thread (in case some
parameters have changed such as the list of symbols for which I need quotes)
or I need to exit the application.

Here is my code. The way I disconnect is I test the _run member variable,
which if false indicates that the thread must be exited and the connection
closed, and in this case I set the return from the callback to 0, which
triggers a curl error in curl_easy_perform, but this doesn't seem too clean
to me. Moreover, after I disconnect once using this method and then I
restart the thread and create a new connection (without exiting the
process), I don't receive any more data, even if all the curl calls return
CURLE_OK. If I restart the application though, then I can, again, open a
connection (and only one) and get data. What could be the reason for this?

typedef std::basic_string< TCHAR > t_string;

size_t CSession::responseCallback(void *ptr, size_t size, size_t nmemb, void
*data)
{
  CSession* pSession = static_cast< CSession* >( data );
  if( pSession -> _run )
  {
    int realsize = size * nmemb;

        // the processing has to be done one character at a time
    for( int n = 0; n < size * nmemb; n++ )
      pSession -> processData( ((char*)ptr)[ n ] );

    return realsize;
  }
  else
    // return a different value than realsize to signal
        // that we want to terminate (it will trigger an error and we'll exit)
    return 0;
}

void CSession::execute( const ExecuteContext& context ) throw
(CurlErrorException)
{
  CURL *curl;
  CURLcode res;

  curl = curl_easy_init();
  if (!curl)
    throw CurlErrorException( _T( "Curl initialization error" ), -1 );

        // make request constructs the quote request for the server
  const t_string request( makeRequest( context ) );
  if( ( res = curl_easy_setopt(curl, CURLOPT_URL, request.c_str() ) ) !=
CURLE_OK )
    throw CurlErrorException( _T( "Curl error in CURLOPT_URL: " ), res );

  if( ( res = curl_easy_setopt(curl, CURLOPT_CAINFO, pCACertFile) ) !=
CURLE_OK )
    throw CurlErrorException( _T( "Curl error in CURLOPT_CAINFO: " ), res );

  if( ( res = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION,
responseCallback ) ) != CURLE_OK )
    throw CurlErrorException( _T( "Curl error in CURLOPT_WRITEFUNCTION: " ),
res );

  if( ( res = curl_easy_setopt(curl, CURLOPT_FILE, (void *)this) ) !=
CURLE_OK )
    throw CurlErrorException( _T( "Curl error in CURLOPT_FILE: " ), res );

  res = curl_easy_perform( curl );
  if( res != CURLE_WRITE_ERROR && res != CURLE_OK )
    throw CurlErrorException( _T( "Curl error in perform: " ), res );

  curl_easy_cleanup(curl);

}

Thanks,

Adrian

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Received on 2004-01-06