Netty Decoder Encoder Error

Question

I've the following Problem. Each time when I send a packet from my Client to my Server with the Same en- and Decoder, I get the following error in my Server console:

    io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(72) + length(8) exceeds writerIndex(77): UnpooledByteBufAllocator$InstrumentedUnpooledUnsafeNoCleanerDirectByteBuf(ridx: 72, widx: 77, cap: 1024)
        at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:461)
        at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:267)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:356)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:342)
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:335)
        at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1294)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:356)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:342)
        at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:911)
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:131)
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:645)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:580)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:497)
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:459)
        at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:131)
        at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:138)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IndexOutOfBoundsException: readerIndex(72) + length(8) exceeds writerIndex(77): UnpooledByteBufAllocator$InstrumentedUnpooledUnsafeNoCleanerDirectByteBuf(ridx: 72, widx: 77, cap: 1024)
        at io.netty.buffer.AbstractByteBuf.checkReadableBytes0(AbstractByteBuf.java:1168)
        at io.netty.buffer.AbstractByteBuf.readLong(AbstractByteBuf.java:651)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:27)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at net.rinet.rnclo.network.encoding.PacketDecoder.decode(PacketDecoder.java:39)
        at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:491)
        at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:430)
        ... 16 more

My Source Looks like this:

Encoder:

import net.rinet.rnclo.network.Packet;
import net.rinet.rnclo.network.PacketRegistry;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;

/**
 * JavaDoc this file!
 *
 * @author Pascal
 * @version 29.10.2017
 */
@AllArgsConstructor
@NoArgsConstructor
public class PacketEncoder extends MessageToByteEncoder<Packet> {
    private PacketRegistry packetRegistry;

    @Override
    protected void encode(ChannelHandlerContext ctx, Packet packet, ByteBuf output) throws Exception {
        long id = this.packetRegistry.getPacketIdByClass(packet.getClass());
        output.writeLong(id);
        packet.write(output);
    }
}

And my Decoder Looks like this:

package net.rinet.rnclo.network.encoding;

import net.rinet.rnclo.network.Packet;
import net.rinet.rnclo.network.PacketRegistry;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;

import java.util.List;

/**
 * JavaDoc this file!
 *
 * @author Pascal
 * @version 29.10.2017
 */
@AllArgsConstructor
@NoArgsConstructor
public class PacketDecoder extends ByteToMessageDecoder {
    private PacketRegistry packetRegistry;

    @Override
    public void decode(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf, List<Object> outputList) throws Exception {
        if(byteBuf.isReadable(2)) {
            long id = byteBuf.readLong();

            if(packetRegistry.checkPacketId(id)) {
                Class<? extends Packet> packetClass = packetRegistry.getPacketClassById(id);
                Packet receivedPacket = packetClass.newInstance();
                try {
                    receivedPacket.read(byteBuf);
                } catch (Throwable t) {
                    t.printStackTrace();
                }
                outputList.add(receivedPacket);
            } else {
                decode(channelHandlerContext, byteBuf, outputList);
            }
        }
    }
}

My Packet Looks like this: https://hastebin.com/atirenevuw.java

I'm really glad about every helpful answer! Pascal

Answer 1

You’re checking to see if you can read 2 bytes, but then you read 8 bytes.

Change this

        if(byteBuf.isReadable(2)) {
            long id = byteBuf.readLong();

To

        if(byteBuf.isReadable(8)) {
            long id = byteBuf.readLong();