Chat

Package Specification Summary for Package: chat

Bug Tracker Summary for Package: chat

Code Metrics Summary for Package: chat

The chat package is currently using two different chat engines:

1. The Java applet and the Java chat server, or
2. the Ajax based chat class from xotcl-core

If no xotcl-core is installed, one can only use the version with Java applet. If xotcl-core is installed, one has to option to choose between both engines via parameter.

In essence, the Ajax based variant is the chat implementation from xowiki plus chat room management and a list of the currently connected users. Originally, the AJAX-based chat class (::xo::Chat) was developed for xowiki, but later moved to xotcl-core such that the chat package does not need a dependency on xotcl-core and xowiki.

Actually, the chat support in xowiki contains a different variety of AJAX based communication strategies:

1. Polling mode (the web browser queries via AJAX in definable intervals the server, and checks, if there is some new information available), and
2. Streaming mode (the client opens a connection to the server, the server pushes the information back to the client. xowiki chat supports two different sub-modes:
   1. streaming of JSON objects via asynchronous AJAX sockets, or
   2. scripted streaming, where the browser loads HTML with embedded script tags in the background from a hidden iframe

Both (2a) and (2b) require libthread installed and NaviServer. However, the advantage of the streaming approaches is that they are much faster in the look and feel and that they are better scalable on sites with a high load. 2a works only on Firefox (not in current versions of IE or Safari) and has the advantage over 2b that the browser does not show the background activity (no spinning wheel in Firefox). 2b is more robust and works with Safari, IE and Firefox (the information about the browser support is from 2006, and most probably different today). Both streaming modes implement, what is sometimes called COMET.

When the chat package uses the ::xo::Chat, it uses it only in currently only polling mode, which has the least requirements. This has been as well tested with (Firefox, IE and Safari).