Here is a small guide on how to get a multiplayer session with the session server working from behind a router. When a multiplayer server is started on a local network (behind a router) there are some special settings you will need to do to be able to reach the session from the outside (the internet).
First of all before starting the multiplayer server you will need to check the 'register session' and 'use gateway' checkboxes. The 'register session' checkbox ensures the session will be registered to the session server, this will make finding the session in Motorboat Simulator easier. The 'use gateway' option is very important. This will tell the server that the session is being played from behind a router/gateway. Once you've checked the 'use gateway' option you will also have to enter the gateway address. This is the IP address you use to access the internet, typically the IP address of your router/gateway and not the IP address of the computer the server is running on. The last and most important step is adding a port forward to your router. The Motorboat Simulator Server is listening for new clients on the port entered in 'server port'. Routers usually block most ports from the outside so it's important the server port is forwarded to you server on your local computer (your local IP address). For more details on how to forward a port on your router you will need to check the user manual of your router.
We hope this will help in setting up a proper multiplayer session and registering it to the session server.