GMnet - Manual

2. PLUS - Setup GMnet PUNCH

If you want GMnet ENGINE can be used to connect players even if the do not forward ports in their firewall.

Please note, that you need GMnet ENGINE for this, simply using GMnet CORE is not enough. If you downloaded GMnet ENGINE from the Game Maker Marketplace, you are good to go (See the site on version differences for more information).

To understand this, you need to know, that whenever you want to play a game with someone there are three options:

Dedicated servers to play on, like most shooters have
Forwarding a port on the servers firewall, most common when playing strategy games or hosting an own dedicated server of some game
"Hole-Punching" - GMnet PUNCH, which ships with GMnet ENGINE version, allows UDP Hole Punching. This technique allows two players to connect to each other even when no ports are forwarded at all. This works most of the time, however not allways. Especially in mobile networks or buisness networks that might fail. Hole Punching is often used by many games where multiplayer should be easy to do by the user.

That means if you DISABLE GMnet PUNCH , your players either can't play together online, only locally, or the server has to open ports.

GMnet PUNCH configuration

In htme_init there are several variables you need to change to use GMnet PUNCH.

self.use_udphp: This is the most obvious one. Set this to true, to enable GMnet PUNCH.

self.udphp_master_ip and self.udphp_master_port: You need to set these to the ip and the port of your mediation server. What a mediation server is, is explained in the next section. You basically need to host a server, to which server and clients connect to share their information.

self.udphp_rctintv: How often (in steps) the server should reconnect to the mediation server to make sure it is still connected. It is important that the server is connected to the mediation server, so don't set this too high. The default option should be fine.

If you don't have a server yet you can use the ip 95.85.63.183 and the port 6510 for testing only.

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