JavaScript Client

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Client/Server application written in JavaScript for portability

1 Usage Instructions
2 Technical Information
3 Why JavaScript
4 Requirements
5 Compatibility
6 External Links

[edit] Usage Instructions

Click on the buttons for information and links about each DNSBL
Enter ip-address or hostname and click on "Lookup"
Problematic entries (from the view of a mailserver at this address) will be colored red
enter another ip or host to continue

[edit] Technical Information

The client consists of one static HTML-page, and one JavaScript-program which dynamically fills the page.

Since JavaScript cant do DNS-queries the client imports the results as JavaScript-Variables from the server.

The query-string (ip-address or hostname) sent from the browser to the server will be encrypted with RC4 and uses a variable key, mainly to protect the server from robots and discourage scripting.

Once the variables are imported the client does not need to contact the server, except for the Logos unless they are already cached.

Repeated lookups for the same key will be also answered from the browsers cache without involvment of the server. This is very fast, and a delay had to be impelemnted to limit the confusion ;)

Static examples of the data for: 127.0.0.2 example.com
(in HTML, need to disable JavaScript first, and view source)

[edit] Why JavaScript

Its the only code which runs on all major operating systems and most modern browsers.

JavaScript has een selected after through evaluation of all possibilities.

Java might have been an alternative, but its also not able to make DNS-queries and a real hog (at least on my old P700-Notebook).

The only way would be with ActiveX, but thats out of question.

[edit] Requirements

JavaScript Varsion 1.5 and W3C-DOM
IFrame support required, Cookies optional
Strictly standards-compliant browsers may break, since the page claims a DOCTYPE that it does not conform to.