Why does netty keep spitting out this error?

I have a game, where I already have coded a networking system. I have packets and all that.. But my server and my client keep spitting out errors? I want to know how to fix this issue.

My client keeps spitting out:

Jun 13, 2020 10:45:45 AM io.netty.util.ResourceLeakDetector reportTracedLeak
SEVERE: LEAK: ByteBuf.release() was not called before it's garbage-collected. See https://netty.io/wiki/reference-counted-objects.html for more information.
Recent access records: 
Created at:
    io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:363)
    io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:187)
    io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:178)
    io.netty.buffer.AbstractByteBufAllocator.ioBuffer(AbstractByteBufAllocator.java:139)
    io.netty.channel.DefaultMaxMessagesRecvByteBufAllocator$MaxMessageHandle.allocate(DefaultMaxMessagesRecvByteBufAllocator.java:114)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:147)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:714)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.lang.Thread.run(Thread.java:748)

My server keeps spitting out:

java.io.StreamCorruptedException: invalid stream header: CD7A4195
    at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:899)
    at java.io.ObjectInputStream.<init>(ObjectInputStream.java:357)
    at io.github.retrooper.comborex.networking.Packet.encode(Packet.java:30)
    at io.github.retrooper.comborex.networking.handler.ServerHandler.channelRead(ServerHandler.java:93)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:714)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.lang.Thread.run(Thread.java:748)

My server says the error is coming from the last line on this method:

  public static Object encode(final byte[] data) throws IOException, ClassNotFoundException {
        return new ObjectInputStream(new ByteArrayInputStream(data)).readObject();
  }

This is how I decode and encode my packets:

 public static byte[] decode(Packet packet) throws IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(packet);
        oos.flush();
        return bos.toByteArray();
    }

    public static Object encode(final byte[] data) throws IOException, ClassNotFoundException {
        return new ObjectInputStream(new ByteArrayInputStream(data)).readObject();
    }

    public static ByteBuf asByteBuf(Packet packet) throws IOException {
        byte[] arr = decode(packet);
        return Unpooled.copiedBuffer(arr);
    }

I do this both client and server side. The server and client are both running on java version 8!

Please can someone explain why this issue is happening and what I might be doing wrong?

Here is my server side channelRead function:

  @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        final ByteBuf buf = (ByteBuf) msg;
        final int len = buf.readableBytes();
        final byte[] bytes;
        final int offset;
        if (buf.hasArray()) {
            bytes = buf.array();
            offset = buf.arrayOffset();
        } else {
            bytes = new byte[len];
            buf.getBytes(buf.readerIndex(), bytes);
            offset = 0;
        }
        final Packet packet;
        try {
            packet = (Packet) Packet.encode(bytes);
        } catch (Exception ex) {
            ex.printStackTrace();
            return;
        }
        handlePackets(ctx, packet, buf);
    }