Netplay is a feature that allows networked multiplayer with some emulators via peer-to-peer (P2P) networking to reduce network latency, to ensure the best possible experience by continuously synchronizing multiple instances running the same emulation kernel and content.
You also have the possibility to have people joining in spectator mode (additional latency).
Online gaming on our old consoles that didn't even know this capability yet!
"Failed to Initialize Netplay" often means that you were unable to connect to the host. Confirm that you have the correct IP address for the Host and that the Host has started hosting a NetPlay session. Tell the host to check if its host-based firewall allows RetroArch to accept connections and confirm that port forwarding is working.
"Port Mapping Failed" probably indicates a UPnP port forwarding problem.
If you can manually configure your network gateway to forward TCP port 55435 to the local network IP address of your RetroArch device, you can do so. You can also enable the use of a relay server (adds latency).
There are 2 possibilities:
Insufficient internet connection
Your port does not open automatically
or
or as a last resort
Check that your cores are in adequacy with your machine (PC, Raspberry Pi or other). Moreover, some machines only support the client function.
Yes, both the host and the client must open ports properly.
There is a backup option that can be used by those who do not want to open their ports (NETPLAY MITM function).
No, the performance requirements of these consoles make netplay difficult.
No, RetroArch netplay is not a cable emulation.
GB, GBC, GBA and PSP are currently not possible with our implementation.
But, a notable exception is the same GB / GBC game (Netplay via TGB-Dual and Sameboy cores).
So Pokémon exchanges and the like are not possible.