CS620: WWWChat

Short Description

A given URL serves as a centralized discussion location. It also maintains a history of the discussion. This is useful to help new visitors get up to speed in a discussion by reading past messages, and is useful as a log/archive of the discussion. Discussion logs are permanent - users could visit this URL, and view messages that were typed days, weeks, or even years ago, if the administrator in charge does not remove entries.

Mechanically, it would involve a user visiting the page, and being presented with the discussion box already showing the most recent talk lines. The user also has an input field and submit button, which are used to add messages to the discussion.

In many respects, this project is like a local newsgroup. However a 'live' feature has been added (i.e., browsers update new messages without user interaction) making this program more similar to a chat or talk program (e.g., IRC or UNIX talk).

What Has Been Achieved

The following features were implemented.

Users can limit the amount of historical chat lines to be retrieved.
Site level security was implemented. The list maintainer can restrict access to certain cites, specified by their IP address. Users will either have no access, read-only, or read and posting ability (known as Full Interactive Mode).
The user's chosen nickname is attached to every message they send.
All messages are date and time stamped.
The chat board dynamically updates the clients' displays with new messages periodially.
Error checking for the following:
- A valid user name must be selected.
- A valid choice of lines to display must be selected.
- User is presented with warning if their browser does not appear to support features needed by the project. Specifically, the dynamic refresh (i.e., client pull) is a Netscape enhancement.

Which Techniques Were Used

The project was coded using the most accepted and appropriate tools for World Wide Web programming, namely perl scripts, hypertext markup language (HTML) and some c++.

Perl scripts are the popular method of CGI programming. The CGI (Common Gateway Interface) provides a means of executing code on the WWW server. The end result of such programming is HTML code that is communicated to the client's browser via HTTP (Hyper Text Transfer Protocol).

TCP/IP was utilized in order to poll the World Wide Web server of the user for some of the information required, namely their IP address (used in the security check) and their type of browser. The latter was important because this program uses a forced refresh in order to simulate the interactive feel of "IRC" or "talk". This refresh is possible with Netscape but with other browsers (such as Mosaic), it will not occur.

The CGI sources and data files reside in a protected directory on the WWW Server. Visitors are not able to view sources, which discourages unauthorized hacking. Visitors are also unable to modify nor view the user and message lists outside of the application. Such security is imposed by both cautious setting of permissions on data files and executables, and by allowing access of data only though executables with a manipulated user id.

Authors

Jack Scott Kaye, scotty@cs.uwm.edu
Jim Urbas, jimu@cs.uwm.edu