RetroArch 1.17 expands Netplay to support playing multiplayer games that were originally played on two or more separate consoles or computers connected together. This is currently supported by two cores: DOSBox Pure and gpSP.
In DOSBox Pure it is now possible to play DOS and early Windows multiplayer games that used IPX, Ethernet or a modem over the internet.
In gpSP, games that support the Wireless Adapter can also benefit from this feature, although only a subset of games work well at the moment (including Pokemon Fire Red/Green Leaf/Emerald). Those curious about more details can read David G.F.’s article about the gpSP implementation here.
In order to use this new functionality just use the regular Netplay menu, where you can host and/or join netplay games. It works seamless with the existing Netplay feature (including lobbies) with no additional settings required. Make sure however, that you use the same or compatible games, since this won’t be automatically enforced.