Whenever I load up my singleplayer world in a custom modpack using NeoForge, the game just kicks me out, and it seems to think I am playing in a multiplayer server. This is the error code (more like a "connection lost" code):

 

Internal exception:

io.netty.handler.codec.EncoderException:

'void com.simibubi.create.content.processing.recipe ProcessingOutput.write(net.minecraft.network.RegistryFriendlyByteBuf)'

Edited March 14Mar 14 by natenoir

Neoforge is not the same as Forge, you would probably get better results asking for help wherever Neoforge support is given.

Also, single player games are essentially local multiplayer games, there's a client and a server running, just both on the same computer. That's why the "open to LAN" button works.

Always post full logs when asking for support (that doesn't change between Forge/Neoforge, or anything for that matter), they likely contain information that would help determine the issue, even if you don't recognize the usefulness of it.

Thank you.

The reason I didn't post the log was that the game didn't crash, the "server" did.