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Firewallfriendly Messenger

What's it?

Do you want use ICQ or AOL instant messenger but your company has an paranoid system administrator that blocks nearly every port?

Here't the solution. This little piece of software let's you communicate through the firewall because it uses 100% pure HTML + Java-Applets. Just enter you username and you can send messages to other users, maybe to arrange a chat in a HTML chatroom like

This version contains no password protection, so please be aware that everyboy who nows your username can read your messages. Once you received a message, it will be deleted.

This is an early version, it will change in the future. It is not intended as an full functional chatserver, only a messenger service.

Everything is freeware.


Please type in your nickname in the textfield that appears at startup. Then you can see the applet.

By default, all people that are online are receiving your messages. If you don't want everybody to see what you type, change the state of the 'all' checkbox and mark the receivers you want to send the messages.

The received messages are updated every 3 seconds in the beginning. After some time the rate decreases until you type in a message.

If you want to get informed that somebody send you a message, you can change the value of the 'Alert combo'

From time to time, a message 'Couldn't connect to server' appears. The reason is that the host for my CGI scripts tries sometimes to redirect a request to another server, but this is not allowed by the applet. Just ignore it.



Applet and Executable

For Programmers

The Chat-Applet consists of two parts. On the client side is the applet that provides the graphical user interface. On the server side is a Perl script that takes the messages to send as a parameter and returns the messages for each user to receive.

In this way, it appears for a firewall as a simple HTML request that will not be blocked. A disadvantage of this method is that the chat parties can't communicate together in a direct connection. So a server is needed and also the chat clients have to poll every few seconds to find out if there are new messages available. This causes a lot of overhead.

Maybe I write a version in the future, that communicates through port 80 between the clients. Don't know why firewalls are so restrictive if workarounds are so easy to program.

Michael Habermann