This issue shows that server ip for test is bound to the local address not real address. so that each agent in the other network zone can not attach the controller.
It's because some linux system returns not predictable address for InetAddress.getLocalAddress().
This issue comes from The Grinder and it's very common in java and linux combination and I've tried to fix this as much as possible by resolving real address calling google.com.
However still there are some missing point in which a controller fails to bind the socket to listen.