Everything old is new again!
CC's network message implementation has gone through several iterations:
- Originally network messages were implemented with a single class,
which held an packet id/type and and opaque blobs of data (as
string/int/byte/NBT arrays), and a big switch statement to decode and
process this data.
- In 42d3901ee3, we split the messages
into different classes all inheriting from NetworkMessage - this bit
we've stuck with ever since.
Each packet had a `getId(): int` method, which returned the
discriminator for this packet.
- However, getId() was only used when registering the packet, not when
sending, and so in ce0685c31f we
removed it, just passing in a constant integer at registration
instead.
- In 53abe5e56e, we made some relatively
minor changes to make the code more multi-loader/split-source
friendly. However, this meant when we finally came to add Fabric
support (8152f19b6e), we had to
re-implement a lot of Forge's network code.
In 1.20.4, Forge moves to a system much closer to Fabric's (and indeed,
Minecraft's own CustomPacketPayload), and so it makes sense to adapt to
that now. As such, we:
- Add a new MessageType interface. This is implemented by the
loader-specific modules, and holds whatever information is needed to
register the packet (e.g. discriminator, reader function).
- Each NetworkMessage now has a type(): MessageType<?> function. This
is used by the Fabric networking code (and for NeoForge's on 1.20.4)
instead of a class lookup.
- NetworkMessages now creates/stores these MessageType<T>s (much like
we'd do for registries), and provides getters for the
clientbound/serverbound messages. Mod initialisers then call these
getters to register packets.
- For Forge, this is relatively unchanged. For Fabric, we now
`FabricPacket`s.
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