Is VASSAL supposed to work if two or more players are behind a firewall, and at least one isn’t behind the same firewall? Two friends and I attempted a couple games tonight; they are both behind the same firewall with the same external IP, and I am at my own internet IP behind my own firewall. In both games we tried, my view of the game was fine, but both of my friends saw an increasing number of duplicates–cards, counters, the works. Starting a new game quickly resulted in the same.

The network code isn’t open is it? If not, that’s a shame, as all of us are in the mood to go to the source to examine this problem ourselves…

All of the code is open. We’d be grateful for the help, if you’re interested
in doing some networking troubleshooting. You can check out the source from

Rodney is the one who’s most familiar with the networking code. Hopefully
this will get his attention.

Of course, the firewall may simply prevent a remote connection outright, but if the firewall allows the connection, then everything else ought to work the same. I can’t see how it could cause duplicate counters unless maybe one of the clients is re-sending transmissions. One thing to try if you want to replicate the bug is to write a logfile during your online session. If you see duplicates when replaying the logfile then it’s a bug that’s not related to the network code.

The client-side network code is open as of version 3.0, so you can set a breakpoint in NodeClient.handleMessageFromServer() if you want to track all incoming messages.


Post generated using Mail2Forum (

Many thanks. We’ll take a closer look.