How do I add Protobuf Encoder/Decoder to existing http netty server?

I'm new to Netty and the title might not make much sense but here's what I'm trying to do. We have an existing Netty server for normal REST APIs. We're trying to experiment with Protobuf and we thought we would just hack the existing server to add ProtobufEncoder/Decoder and we would be able to just run them both in parallel. It doesn't seem to work that way.

Here's my initChannel

@Override
    protected void initChannel(SocketChannel ch) throws Exception
    {
        ChannelPipeline pipeline = ch.pipeline();

        /**
         * Protobuf
         */
        pipeline.addLast(new LengthFieldBasedFrameDecoder(1024, 0, 4, 0, 4));
        //Decode the message sent by the client
        pipeline.addLast(new ProtobufDecoder(HelloRequest.getDefaultInstance()));
        // encoded
        pipeline.addLast(new LengthFieldPrepender(4));
        pipeline.addLast(new ProtobufEncoder());
        //  Register the handler
        pipeline.addLast(new ServerHandler());
        /**
         * End Protobuf
         */

        pipeline.addLast(CODEC, new HttpServerCodec());
        pipeline.addLast(DECOMPRESSOR, new HttpContentDecompressor());
        if (serverCompressHttpResponses_) {
            pipeline.addLast(COMPRESSOR, new HttpContentCompressor());
        }
        pipeline.addLast(AGGREGATOR, new HttpObjectAggregator(maxContentLength_));
        if (maxKeepAliveRequests_ >= 0 || maxKeepAliveTTLSeconds_ >= 0) {
            pipeline.addLast(KA_HANDLER, new KeepAliveHandler(maxKeepAliveRequests_, maxKeepAliveTTLSeconds_));
        }
        pipeline.addLast(ROUTER, routerProvider_.get());
        if (countActiveConnections_) {
            pipeline.addLast(CONNECTION_COUNTER, new ConnectionCounter());
        }
    }

We have a HttpRouter which extends ChannelDuplexHandler to handle path like /query and /ping

The problem is if I have the section for Protobuf before all of the Http stuff, the server will hang on /ping but the protobuf works as expected. However, if I moved the section Protobuf to be after line pipeline.addLast(ROUTER, routerProvider_.get()); then /ping works as usual but the server would hang on RPC call from Client with Protobuf.

Here's the code for ServerHandler

public class ServerHandler extends SimpleChannelInboundHandler<Message>
{
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Message msg) throws Exception
    {
        //  Print out the message directly
        System.out.println(msg.getClass());
        HelloReply response = null;
        if (msg instanceof HelloRequest) {
            HelloRequest clientMsg = (HelloRequest) msg;
            System.out.println(ctx.channel().remoteAddress() + " Say : " + clientMsg.getName());
            response = HelloReply.newBuilder().setMessage("test").build();
        } else {
            response = HelloReply.newBuilder().setMessage("client message is illegal").build();
            System.out.println("client message is illegal");
        }
        //  Return to the client message-I have received your message
        ctx.writeAndFlush(response);
    }
}

My question is if I will be able to have the same Netty server does REST API and Protobuf on the same port? Or it's just not possible?