I wrote that client, it was based on version 1.0.4 and protocol version 10010.
If you check out the project from Github, you have the same problem?
(remember to change the username, password, chain_name etc in App.java class)
Can you elaborate more on your network setup? If I understood correctly you have the multichain running on a node and you want to connect to it from another node?
Also, if you try first from the command line, using mutlichain-cli can you get a response?
Thank you for trying the client. Hope we can help you find the solution to the problem.