How do I set up Peer-to-Peer connection

My son and I are trying to arrange a game of Kingmaker using a Peer-to-peer facility but we have both tried (separately) to set up the connection and on each occasion our IP addresses have failed to respond. We have followed the manual instructions carefully but no joy. Can anyone suggest what we might be doing wrong, please?


There are a whole host of potential issues–chief among them would be firewall software (either built into your operating system, depending on what you have) or a 3rd party program you might be running. You’d want to either temporarily disable these or determine which port VASSAL peer-to-peer requires (can’t recall offhand) make sure exceptions are in place to allow traffic through on both machines.

Hi Joel:
I am running Windows 10 and Avast Business Security software. Vassal tells me I should use Port 5050 - whatever that means - (and my son the same). I’ve no idea how to set up the firewall system(s) to allow traffic (suppliers of such software don’t seem to think a proper manual is necessary any more) because, sadly, neither my son nor I are “tecchies” so I am thrown back on trying to get help from forums like this one. Anyway, thanks for the heads-up. I’ll see what I can find about allowing the traffic through the firewall software - wish me luck!


Mike, Are you trying to play over the internet? If so, then each_player needs to configure his internet gateway router to direct incoming traffic on port 5050 to the LAN IP of the machine running VASSAL.

First each player needs to know the LAN IP address of the computer running VASSAL, and you also need the IP address of the Default Gateway.

Open a Command Prompt and type ipconfig
Remember the IP address and Default Gateway that are shown.
Let’s say, for example, it reports a LAN IP of and a Default Gateway of

Open a web browser and type (your default gateway) in the address bar. Then log in to your router.

In the “port forwarding” configuration set it to send all traffic on port 5050 to (your VASSAL machine’s LAN IP). Save that configuration.

Each player should also know his current WAN IP address (the IP address of your router as seen from the internet).
Just go to and it will be displayed.

At this point the players should be able to follow the instructions on pages 8 and 9 of the VASSAL userguide “Launching a game” knowing that any invitations should go to the WAN IP of the other player (not the LAN IP).