When you trying to connect to a non-RMI host:port like:

% jconsole webcache.sfbay.sun.com:8080
or
% jconsole www.ibm.com:80

there is a pause (usually from 3 to 20 seconds) before connection dialog appears notifying of error. Nothing is displayed during this pause and user has no idea whether jconsole is trying to connect or it has simply ignored the URL from Connection dialog or command-line.

If possible, please implement some kind of connecting progress window.