LightInjector

A light yet complete and fast packet injector for Spigot servers.

Tested versions

LightInjector has been successfully tested on 1.8-1.21.3 server versions.

How to use

Copy and paste the LightInjector class inside your plugin or shade it using maven.

Maven Instructions

<repositories>
    <repository>
        <id>fren_gor</id>
        <url>https://nexus.frengor.com/repository/public/</url>
    </repository>
</repositories>

<dependency>
    <groupId>com.frengor</groupId>
    <artifactId>lightinjector</artifactId>
    <version>1.0.4</version>
    <scope>compile</scope>
</dependency>

It's suggested to shade it:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>3.3.0</version>

    <configuration>
        <relocation>
            <pattern>com.fren_gor.lightInjector</pattern>
            <shadedPattern>your.shaded.path.com.fren_gor.lightInjector</shadedPattern>
        </relocation>
    </configuration>

    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>shade</goal>
            </goals>
        </execution>
    </executions>
</plugin>

Extend the LightInjector class and implement the onPacketReceiveAsync and onPacketSendAsync methods. These methods will be called, respectively, when the server receives/sends a packet from/to a player.

public class YourClass extends LightInjector {

    public YourClass(@NotNull Plugin plugin) {
        super(plugin); // This initializes the injector when YourClass will be constructed
    }

    @Override
    protected @Nullable Object onPacketReceiveAsync(@Nullable Player sender, @NotNull Channel channel, @NotNull Object nmsPacket) {
        // This will be called (asynchronously) when the server receives a packet from a player
        // The sender may be null for early login packets, so always check for it

        // Return the packet which will be received from the server, which can be different from the original packet.
        // Return null to cancel the packet.
        return nmsPacket;
    }

    @Override
    protected @Nullable Object onPacketSendAsync(@Nullable Player receiver, @NotNull Channel channel, @NotNull Object nmsPacket) {
        // This will be called (asynchronously) when the server sends a packet to a player
        // The receiver may be null for early login packets, so always check for it

        // Return the packet which will be sent to the player, which can be different from the original packet.
        // Return null to cancel the packet.
        return nmsPacket;
    }
}

Then create an instance of YourClass to start listening to packets.

public class MainClass extends JavaPlugin {
    private YourClass injector;

    @Override
    public void onEnable() {
        injector = new YourClass(this);
    }
}

LightInjector will deinitialize itself automatically when the plugin disables, or you can do so manually by using the close() method.
Packets will not be intercepted anymore after calling the close() method.

Calling the close() method manually is usually not necessary, unless you want to stop listening to packets before your plugin disables.

License

This project is licensed under the MIT license.