Working with Protocols

Protocols are collections of packets that are used to communicate between the client and the server.
Addons can create custom protocols to send and receive custom packets.
The LabyMod 4 Server API provides the LabyMod Protocol that is used to communicate with the LabyMod client.

The LabyMod Protocol

The LabyMod Protocol is the default protocol, it contains all official features that servers can use to customize the experience of LabyMod players.

A collection of all available features can be found here.

Registering Handlers

To register a packet handler in the LabyMod Protocol, you first need to create a new class implementing the PacketHandler interface. We'll use the VersionLoginPacket in the following example.

import net.labymod.serverapi.api.packet.PacketHandler;
import net.labymod.serverapi.core.packet.serverbound.login.VersionLoginPacket;
import org.jetbrains.annotations.NotNull;

import java.util.UUID;

public class VersionLoginPacketHandler implements PacketHandler<VersionLoginPacket> {

  /**
   * Handles the VersionLoginPacket
   * 
   * @param sender the unique id of the sender of the packet
   * @param packet the packet that was sent
   */
  @Override
  public void handle(@NotNull UUID sender, @NotNull VersionLoginPacket packet) {
    // Perform logic to handle the packet
  }
}

After creating the handler, you can register it in the LabyMod Protocol.

// Get the LabyModProtocol
LabyModProtocol labyModProtocol = LabyModProtocolService.get().labyModProtocol();

// Register the handler
labyModProtocol.registerHandler(
    VersionLoginPacket.class, // The packet class
    new VersionLoginPacketHandler() // Object of the handler (can also be a lambda)
);

Create a Custom Protocol

To create a custom protocol, you can create a new instance of AddonProtocol by calling the constructor with the protocol service and namespace as parameters. Then register the protocol in the ProtocolRegistry.

// Get the Protocol Service
LabyModProtocolService protocolService = LabyModProtocolService.get();

// Create a new AddonProtocol
AddonProtocol protocol = new AddonProtocol(protocolService, "example");

// Register the protocol
protocolService.registry().registerProtocol(protocol);

Register a Packet

To register a packet, you first need to create a Packet. After doing that, you can just register the packet in the protocol.

With Handler Without Handler

// Register the Packet with handler
protocol.registerPacket(
    0, // the id of the packet. Must be unique in the protocol on both sides
    ExamplePacket.class, // the class of the packet
    Direction.CLIENTBOUND, // the direction of the packet. Can also be SERVERBOUND or BOTH
    new ExamplePacketHandler() // the handler of the packet
);

// Register the Packet without handler. Handler can be registered later.
// See above for registering a handler separately
protocol.registerPacket(
    0, // the id of the packet. Must be unique in the protocol on both sides
    ExamplePacket.class, // the class of the packet
    Direction.CLIENTBOUND // the direction of the packet. Can also be SERVERBOUND or BOTH
);