Cannot register remote control to Selenium Hub

I got this problem when I tried to register the remote control to Selenium Hub.

Here is the ip info: RC: 172.16.0.90 HUB: 172.16.0.121

Step: 1. "ant launch-hub" on Hub Machine 2. "ant -Dport=5555 -Dhost=172.16.0.90 -Dhuburl=http://172.16.0.121:4444 lanuch-remote-control" on RC Machine.

The error message is that "Could not contact the Selenium HUb at 'http://localhost:4444' : Connection refused..."

Why it is connecting to "localhost"? Did I do the wrong开发者_开发知识库 step or wrong command? Thanks a lot for the help.

The argument is -DhubURL, not -Dhuburl.