From Windows machines I download and start join.exe end everything went well. 

But from Linux machines, where the java app is executed, some keys sent from the support computer aren't working, like the Enter key and Backspace. In some cases, e. g. in a x-terminal, pressing ctrl+m can be used as a replacement for the Enter key and ctrl+h as replacement for Backspace. But this doesn't work in all cases, e. g. when the keys are intercepted by the program running in the foreground.

I tried with different Java browser plugins (IBM Java 7, icedtea 7, Oracle JRE 8) - all the same.

Is there any solution to this?