Protocol Control

Under development and not stable!

A minimal packet manipulation library for Sponge.

Prerequisites

• Java 8

Building

Note: If you do not have Gradle installed then use ./gradlew for Unix systems or Git Bash and gradlew.bat for Windows systems in place of any ‘gradle’ command.

In order to build ProtocolControl you simply need to run the gradle command. You can find the compiled JAR file in ./build/libs labeled similarly to ‘protocolcontrol-x.x.x-SNAPSHOT.jar’.

Dependency

Using ProtocolControl in your plugin requires you to use ForgeGradle and add ProtocolControl as a compile-time dependency.

repositories {
  maven { url "https://repo.ichorpowered.com/repository/maven-public" }
}

dependencies {
  compile "com.ichorpowered:protocolcontrol:0.0.2"
}

Usage

To get started, you will need to get the instance of the ProtocolService from the ServiceManager.

Optional<ProtocolService> protocolService = Sponge.getServiceManager().provide(ProtocolService.class);

Creating a Listener

To create a packet listener, you need to add the @Subscribe annotation on your listener methods, with a parameter for PacketEvent with a generic argument of the Packet<?> type you are listening for.

@Subscribe
public void onLoginEvent(PacketEvent<SPacketLoginSuccess> event) {
  ...
}

You can register the listener by passing in the listener object to ProtocolEvent#register. You can also unregister the listener with ProtocolEvent#unregister.

The ProtocolEvent is acquired from ProtocolService#events.

Manipulating a Packet

The event has a method to get the ChannelProfile the packet is going to or coming from and the PacketDirection.

You have access to the original instance of the packet as well as a way to override the packet.

@Subscribe
public void onLoginEvent(PacketEvent<SPacketLoginSuccess> event) {
  SPacketLoginSuccess packet = event.packet(); // Gets the packet instance.
  event.packet(...); // Override the packet instance.
}

You can also prevent a packet from reaching its destination by cancelling the event.

@Subscribe
public void onLoginEvent(PacketEvent<SPacketLoginSuccess> event) {
  if (!event.cancel()) event.cancel(true); // If the packet is not already cancelled, cancel it.
}

Wrapping a Packet

PacketRemapper provides an optional wrapper for your packet, which provides methods to get and set the fields for a packet. This is particularly useful but not limited to packets that do not provide convenient getters or setters. You just need to know the field type and the index for the field of that type in order to use them.

@Subscribe
public void onLoginEvent(PacketEvent<SPacketLoginSuccess> event) {
  PacketRemapper.Wrapper<SPacketLoginSuccess> wrapper = this.remapper.wrap(event.packet());
  GameProfile profile = wrapper.<GameProfile>get(GameProfile.class, 0); // Gets the game profile.
  wrapper.<GameProfile>set(GameProfile.class, 0, ...); // Sets the game profile.
}

The PacketRemapper is acquired from ProtocolService#remapper.

Sending a Packet

You can send a new packet to the client or to the server using the ChannelProfile#send method.

@Listener
public void onPlayerMove(final MoveEntityEvent event, final @First Player player) {
  final Location<World> location = player.getLocation();
  final ChannelProfile profile = this.protocolChannel.profile(player.getUniqueId());
    
  try {
    final PacketRemapper.Wrapped<SPacketBlockChange> blockChange = this.remapper.wrap(new SPacketBlockChange());
    blockChange.set(BlockPos.class, 0, new BlockPos(location.getBlockX(), location.getBlockY(), location.getBlockZ()));
    blockChange.set(IBlockState.class, 0, (IBlockState) BlockTypes.WATER.getDefaultState());

    profile.send(PacketDirection.OUTGOING, blockChange.packet()); // Sends the block change packet to the client.
  } catch(Throwable throwable) {
    throwable.printStackTrace();
  }
}

The ProtocolChannel is acquired from ProtocolService#channels. You can then grab the players ChannelProfile using ProtocolChannel#profile.