Create Your Own Personal Internet Web-bot

There's no arguing that the Internet lets us access
amazing volumes of information on virtually any subject. However, if you're like
us, you may have found it difficult to filter out unnecessary information from
this enormous repository. Gathering specific facts can be time consuming, with
data usually scattered across many sites. Search engines like Yahoo!, HotBot,
and even Ask Jeeves, have attempted to fill this void, but have been only
partially successful. A recent study found that search engines have indexed less
than 55 percent of the Web. The same study predicted that this percentage would
in fact continue to shrink as the number of new pages on the Internet grows.

In the future, people will probably turn to personal,
automated search programs to find what they need. These Web-bots provide more
targeted and thorough searches. In this article, we'll look at the Web-bot shown
in Figure A, which lets you research any topic on the Internet. Then, we'll
cover a few of the basics you'll need to create a Web-bot fit to rival Jeeves
himself!

To boldly go where no Web-bot has gone before

Next, indicate how thorough a search you want the bot to
conduct in the Search Depth text box. High numbers make for in-depth searches,
but take longer to complete. Lower numbers are less thorough but complete much
quicker. If you have a slow Internet connection and only a few minutes to run
the Web-bot, consider entering a 2 or 3. If you have a fast Internet connection
or have a lot of time (for example, you may be running the program over-night),
enter a higher number like 9 or 10. The Web-bot doesn't care how high you make
this number. As you can see in Figure A, we entered 3 for our search depth.

Full speed ahead, botty

Finally, tell the Web-bot where to start. Search engines
can be good launching points, so if you want to start with one of these, choose
the corresponding option button. If you want to start at a custom URL, click the
Custom URL option button, and then enter the URL in the text box.

Now that we've set the Web-bot's options, we're ready to
launch it. To do so, click Start Search, and then click Yes when the program
asks if you're conducting a new search. That done, the Web-bot races ahead at
warp speed, looking for the information you requested. (OK, that's the last of
the Star Trek references, promise!)

At any time, if you wish to take a closer look at a URL,
just click the Pause button. Then, find a URL in the treeview and right-click on
it. Doing so transports the page into the browser on the right side. The program
also logs email addresses, as well as the URLs, in a local Access 97 database
for your later perusal. We called this database WebAgent.mdb.

The anatomy of a Web-bot

In addition to the controls visible at runtime, Figure B
shows the few controls not visible. As you can see, we've placed an ImageList
and Inet control on the form. Also, the larger box at the very bottom is an
RTFTextbox control. Finally, note that in the main body of the Web-bot, we used
a Treeview to list the Web sites and email addresses, and a Browser control to
display the pages. Now, let's take a look at the more complex features.

Figure B: We'll import HTML pages into the
RTFTextbox control, and then use its Find method to search the HTML for the
selected topic.

Navigating to a Web page

Listing A: Navigating to a URL

Function mNavigateToURL(ByRef rIntInternetControl
_


As Inet, ByRef rbrwsBrowserControl As WebBrowser, _

End Function

Displaying Web pages

rbrwsBrowserControl.Navigate vstrURL

Analyzing a page

?á

• The email addresses located on the page.
  
• The links that exit the page, so the Web-bot can
  continue its journey.

Listing B: The mExtractHTML function

Function mExtractHTML(ByVal vstrStartDelimiter _


As String, ByVal vstrEndDelimiter As String, _

End Function

The functions mcolGetAllUrlsInPage and mcolExtractAllEmailAddressesOnPage
build on the previous function and return the links or email addresses
(respectively) back to the calling routine via a collection. These functions are
smart enough to remove links and email addresses that might appear valid to a
less sophisticated Web-bot, but really wouldn't be applicable. For example, most
email addresses to mailing lists are of the format subscribe@somedomain.com. The
routine weeds these out. Other examples of screened email addresses include
sales@somedomain.com and support@somedomain.com.

Avoiding infinite loops

Second, before going to any new URL, it determines if it
already visited the page. To do so, it calls mblnAlreadyVisiting,
shown in Listing C. If the database contains the URL, then the Web-bot skips the
page, thus short-circuiting the infinite loop.

Listing C: Code to detect duplicate URL

Function mblnAlreadyVisiting(ByVal vstrURL As
String)


Dim objConnection As ADODB.Connection

End Function

Resuming operation after stopping

To allow the user to resume his search, the Web-bot uses
the same URL log that protects against infinite loops to keep track of the
currently visited URL. If the application gets prematurely shut down, it will
simply pick up where it left off.

Conclusion