The latest versions of MS XML shipped with Pocket PC 2003-flavoured devices that expose the XMLHTTP object, which in turn allow exchanging and manipulating data in XML format. Compared to its desktop brother, it's poorly documented in the WinCE help system. Hence, I'll shortly run through IXMLHTTPRequest's methods and properties. It is summarized in the following table. I've used C++ syntax, but VB developers will find only a few differences.

So, all the business looks relatively easy.

Common Working Flow

Similar to other WinInet scenarios, XMLHTTP usually can be used as follows:

• Define and initialize an IXMLHTTPRequest interface instance
• Call an open method to set up a request method (for example, "GET"), URL, sync/async mode, user, and password
• Optionally call a setRequestHeader method to set up all required headers
• Call a send method to send a request to the remote host
• Obtain a response in the desired form; in other words, as a string, XML document, and so forth, by calling the appropriate get_XXX method
• Release the IXMLHTTPRequest object

Following the announced process, the following snippet shows these simple steps:

static TCHAR* g_lpszEndpointURL = _T("http://someserver/alex.xml");

CComQIPtr<IXMLHTTPRequest,&__uuidof(IXMLHTTPRequest)> spXMLHTTP;
HRESULT hr = spXMLHTTP.CoCreateInstance(__uuidof(XMLHTTPRequest));
if ( SUCCEEDED(hr) )
{
   COleVariant vAsync,vUser,vPwd;
   vAsync = VARIANT_FALSE;
   hr = spXMLHTTP->open(CComBSTR(_T("GET")), g_lpszEndpointURL,
                        vAsync, vUser, vPwd);

   COleVariant vBody;
   hr = spXMLHTTP->send(vBody);

   long nStatus = 0;
   hr = spXMLHTTP->get_status(&nStatus);

   if ( nStatus == 200 )
   {
      CComBSTR bstrString;
      hr = spXMLHTTP->get_responseText(&bstrString);

      //process it as needed
      ...
   }
}

The preceding code just takes some XML file pointed to by the g_lpszEndpointURL parameter from the remote host. Obviously, you can use similar "GET" requests to receive some XML data from ASP pages. To call Web Services, the application should use the "POST" method. In this case, you will have to provide all SOAP enveloping manually. I will discuss it later in this article.