Networking and aiming

Packets

NetApi (server and common) and NetClientApi (client) register and send packets the same way on every loader. Register packets from your common init.

On Minecraft 1.21.11 and 26.3 you use the game's own payload types:

NetApi.toClient(MyPayload.TYPE, MyPayload.CODEC);
NetApi.toServer(CastPayload.TYPE, CastPayload.CODEC);

NetApi.receive(CastPayload.TYPE, (payload, context) -> {
    ServerPlayer player = context.player();
});

NetApi.send(player, new MyPayload(1));

On Minecraft 1.20.1 and 1.21.1 you make a packet kind first:

RimuPacket<MyPayload> kind = NetApi.packet(id, MyPayload.class, MyPayload::write, MyPayload::read);

NetApi.toClient(kind);
NetApi.send(player, new MyPayload(1));

Use canSend to check that the other side has your packet.

On the client:

NetClientApi.receive(MyPayload.TYPE, (payload, context) -> {
    // Handle it here
});

NetClientApi.send(new CastPayload(0));

Aiming

AimApi finds what a player is pointing at, on the server.

// The ground under the crosshair
Vec3 spot = AimApi.ground(player, 256.0, 64.0);

// The living entity under the crosshair, or null
LivingEntity target = AimApi.creature(player, 256.0);

ground takes a range and a fallback distance. When the player looks at the sky, it lands that many blocks out in the direction they face. A creature under the crosshair takes priority over the block behind it.