In JamiesWhiteShirt/clothesline-fabric#11, I realized that fabric's network api have no convenience method for mods to opt-out of packet sending to the other side if the other side has no corresponding packet receiver. This causes rejection/client kick from certain servers such as paper. A hook to send only if the packet is identified can ease such conflicts.

I encountered this issue as well here: magneticflux-/fabric-mumblelink-mod#22. There's a corresponding Spigot issue here, which was recently resolved (to some degree at least): SPIGOT-5681.

This is implemented in https://github.com/FabLabsMC/networking-api-v1-draft, a draft repo for #455. Will probably update that pr a bit later with the stuff from the draft repo; you can test out my networking draft for now.

This has been in networking v1, I think?