C / C++ / MFC

// http session
CInternetSession mySession(NULL, 1, PRE_CONFIG_INTERNET_ACCESS, NULL,
                        NULL, 0);
// http connection
CHttpConnection *pHttpConnection;
// http file pointer
CHttpFile       *pHttpFile;
// server url and object.
CString         szServerUrl, szObject;
CString strHeaders = _T("Content-Type: application/x-www-form-urlencoded");

//disable timer
mySession.SetOption(INTERNET_OPTION_CONNECT_TIMEOUT,0xFFFFFFFF,0);

DWORD Post(CString url, CString szFormData, CString & resultString)
{
	// http session
	CInternetSession mySession(NULL, 1, PRE_CONFIG_INTERNET_ACCESS, NULL, 
							NULL, 0);
	// http connection
	CHttpConnection *pHttpConnection;
	// http file pointer
	CHttpFile		*pHttpFile;
	// server url and object.
	CString			szServerUrl, szObject;
	CString strHeaders = _T("Content-Type: application/x-www-form-urlencoded");

	//disable timer
	mySession.SetOption(INTERNET_OPTION_CONNECT_TIMEOUT,0xFFFFFFFF,0);

	// extract server and objects
	szServerUrl = url;
	ExtractObject(szServerUrl,szObject);

	try 
	{
		pHttpConnection = mySession.GetHttpConnection(szServerUrl);	

		if( NULL == pHttpConnection)
		{
			// no exception raised but there is an error. 
			return WEB_ACCESS_UNEXPECTED_ERROR;
		}
	}
	catch (CInternetException *pException)
	{
		char buffer[1023];
		pException->GetErrorMessage(buffer, 1023);
		resultString = buffer;
		return pException->m_dwError;		
	}

	// open request
	try {
		pHttpFile = pHttpConnection->OpenRequest(CHttpConnection::HTTP_VERB_POST, szObject);

		if(NULL == pHttpFile)
		{
			return WEB_ACCESS_UNEXPECTED_ERROR;
		}
	}
	catch(CInternetException *pException)
	{
		char buffer[1023];
		pException->GetErrorMessage(buffer, 1023);
		resultString = buffer;
		return pException->m_dwError;
    }

	// send the request
	try {

		BOOL ret = pHttpFile->SendRequest(strHeaders, (LPVOID)(LPCSTR)szFormData, szFormData.GetLength());

		if( FALSE == ret )
		{
			return WEB_ACCESS_UNEXPECTED_ERROR;
		}
	}
	catch(CInternetException *pException)
	{
		char buffer[1023];
		pException->GetErrorMessage(buffer, 1023);
		resultString = buffer;
		return pException->m_dwError;
	}

	// query status code
	DWORD retCode;
	BOOL ret = pHttpFile->QueryInfoStatusCode(retCode);
	if( FALSE == ret )
	{
		return WEB_ACCESS_QUERY_INFO_ERROR;
	}
	else if( HTTP_STATUS_OK != retCode )
	{
		return retCode;
	}

	char buf[2];
	int bytesRead;
	resultString = "";
	
	while( (bytesRead = pHttpFile->Read(buf, 1)) > 0 )
	{
		resultString += buf[0];
	}
	return WEB_ACCESS_DONE;
}