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HTTP Support

Visual Prolog contains an API to the Internet HyperText Transfer Protocol (HTTP). This is the basic protocol used by the World Wide Web. This API can be used to create WWW client and server utilities as well as Internet Agents in Visual Prolog.

As an example of using the HTTP protocol, we have implemented the WEBAGENT, which is supplied with full source code on the disk. The Web-agent application can monitor given WEB sites and download the content to your hard disk if anything changes. You can also be notified by E-mail if you like. It is quite a useful tool if you don't want to visit the same homepage over and over again to see if its content has changed. The source code is supplied with an example, so you can examine how to develop web-applications in Visual Prolog.

To use the program, compiler it and run it. In the address-columns, type in URLs. Then, in the timer-columns, type in how often these homepages should be checked for change of contents (in minutes). In the Entry Settings, you can specify which person should be e-mailed about changes.

It is necessary to set the options by clicking on the Options-button. Here, you specify the proxy-setting (if any), the resultfile, and which browser to use with the Web-agent.

When all this is done, you can just sit back and wait, or you can push the View Results button to see the homepages that have been  downloaded.