Netty粘包问题TooLongFrameException: Adjusted frame length exceeds

服务器代码初始化部分

ServerBootstrap b = new ServerBootstrap();
		b.option(ChannelOption.SO_BACKLOG, 1024).childOption(ChannelOption.SO_KEEPALIVE, true);
		b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {
			@Override
			public void initChannel(SocketChannel ch) throws Exception {
				ChannelPipeline p = ch.pipeline();
				p.addLast("frameDecoder", new LengthFieldBasedFrameDecoder(2 * 1024 * 1024, 0, 4, 0, 4));
				p.addLast("protobufDecoder", new ProtobufDecoder(PBMsg.getDefaultInstance()));
				p.addLast("frameEncoder", new LengthFieldPrepender(4));// 前4个字节记录长度
				p.addLast("protobufEncoder", new ProtobufEncoder());
				p.addLast(executorGroup, "handler", new ServerHandler());
			}
		});
		b.childOption(ChannelOption.SO_KEEPALIVE, true).option(ChannelOption.SO_BACKLOG, 1024);
		ChannelFuture f = b.bind(port).sync();

客户端网关连上面服务器的初始化代码：

b.group(group).channel(NioSocketChannel.class).option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 1000).handler(new ChannelInitializer<SocketChannel>() {
			@Override
			public void initChannel(SocketChannel ch) throws Exception {
				ChannelPipeline p = ch.pipeline();
				p.addLast("frameDecoder", new LengthFieldBasedFrameDecoder(2 * 1024 * 1024, 0, 4, 0, 4));
				p.addLast("protobufDecoder", new ProtobufDecoder(PB2Msg.getDefaultInstance()));
				p.addLast("frameEncoder", new LengthFieldPrepender(4));// 前4个字节记录长度
				p.addLast("protobufEncoder", new ProtobufEncoder());
				p.addLast("handler", new ClientHandler());
			}
		});

发送代码

//msg是一个PBMsg
clientChannel.writeAndFlush(msg);

异常

io.netty.handler.codec.TooLongFrameException: Adjusted frame length exceeds 2097152: 1079003728 - discarded
	at io.netty.handler.codec.LengthFieldBasedFrameDecoder.fail(LengthFieldBasedFrameDecoder.java:513)
	at io.netty.handler.codec.LengthFieldBasedFrameDecoder.failIfNecessary(LengthFieldBasedFrameDecoder.java:491)
	at io.netty.handler.codec.LengthFieldBasedFrameDecoder.exceededFrameLength(LengthFieldBasedFrameDecoder.java:378)
	at io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:421)
	at io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:334)
	at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:505)
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:444)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:283)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1421)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930)
	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:697)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:632)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:549)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:511)
	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:918)
	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)