The Java Client is still in beta. It mostly works!, but there are some things you should know.
It only makes one connection attempt at a time. If you connect and then receive a NO CARRIER or otherwise lose connection (due to telnet or router TCP timeout, for example) please close out of the java client completely and restart.
If you type and nothing happens, the java client has lost focus. Try Options - Reclaim focus to fix.
I would like to add more functionality to the client, such as cut & paste between operating system, actually make it look like a real program (ProTERM for example for the Apple II), and add architectures (IBM PC and Amiga come to mind.)