I can't tell you much about the implementation of vassal connectivity. A quick test that might indicate that things are badly broken would be to connect your browser to
http://www.vassalengine.org/util/getServerImpl (which is what I think the vassal legacy server connection connects to). That should return something like:
type = node
nodeHost = one.vassalengine.org
nodePort = 5050
If that works, you might try (in a command window) "tracert one.vassalengine.org" (replace tracert with traceroute if you are not using windows). That should produce something like:
traceroute one.vassalengine.org
traceroute to one.vassalengine.org (62.210.178.7), 30 hops max, 60 byte packets
1 10.0.0.1 (10.0.0.1) 0.172 ms 0.159 ms 0.154 ms
2 192.168.1.1 (192.168.1.1) 1.500 ms 1.792 ms 1.790 ms
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 one.vassalengine.org (62.210.178.7) 149.756 ms !X 152.077 ms !X 154.856 ms !X
The values in the route will probably be different.
If that works you have a path to the server.
JR