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Using the Connection Relay Daemon

Created by leo. Last edited by leo, 11 years and 108 days ago. Viewed 26,594 times. #4
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All Java Applets have several security restrictions that prevent a random applet from doing damage on your computer or on the network. Due to this reason it is not possible to open a telnet/ssh connection to any other machine then the one the applet was downloaded from (the webserver).

Sometimes your application is not running on the webserver, in these cases you need some kind of forwarder. Any program, tool or firewall configuration that forwards connections going to a specified port on the webserver to your real targethost and port will do.

We have supplied to simple tools that establish that portforwarding. They run on the webserver (you will need permission from its system administrator).

Single Relay Demon

The first one is the single relaydemon. It can have just one targethost and -port (but it can be used by multiple users at the same time).

It is started on the webserver host by running:

./relayd <localport> <targethost> <targetport>

In the applet you only set the parameter Socket.port to <localport>. <targethost> and <targetport> are the host where the application is.

<localport> can be choosen freely and should be above 1024.

Multiple Relay Demon

This one allows multiple users going to multiple targets (only needed if you have more than one access point). If you have just one targethost and targetport, the single relay demon above works as well!

It is started on the webserver host by running:


It listens on port 31415 by default.

In the applet you have to change the parameters:

Socket.hostthe target host you want to connect to
Socket.portthe target port you want to connect to
Socket.relaythe webserver address

(Note: Both relay demons impose a security risk. Always clear their use with your administrator.)

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