Netty (4) client server communication in the same TCP Session

Question

I need to build a client that initiates a TCP connection with a server and upon response it sends a hand shake request every 10 seconds and gets a response from the server. The server will be able to send another type of request which my client needs to read and act upon. I am using netty 4.0.26.Final.

I have built a client and a dummy server but I am facing an issue which possibly means that there is something I have not understood.

My Client:

    String host = "localhost";
    int port = 9884;
    EventLoopGroup workerGroup = new NioEventLoopGroup();

    try {
        Bootstrap b = new Bootstrap();
        b.group(workerGroup);
        b.channel(NioSocketChannel.class);
        b.option(ChannelOption.SO_KEEPALIVE, true);
        b.handler(new MyChannelPipeline());

        // Start the client.
        ChannelFuture f = b.connect(host, port).sync();

        String line = "line";
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        while (!line.equals("exit")) {
            line = in.readLine();
            if (line == null) {
                break;
            }
        }

        // Wait until the connection is closed.
        f.channel().closeFuture().sync();

    } finally {
        workerGroup.shutdownGracefully();
    }

The ChannelPipleline:

    @Override
public void initChannel(Channel ch) throws Exception {

    ChannelPipeline channelPipeline = ch.pipeline();

    //Encodes every request send from the client to the server
    channelPipeline.addLast("clientRequestEncoder", new ClientRequestEncoder());

    //Implements channelActive and exceptionCaught
    channelPipeline.addLast("initialRequestHandler", new InitialRequestHandler());

    channelPipeline.addLast("byteArrayDecoder", new ByteArrayDecoder());

    channelPipeline.addLast("serverResponseDecoder", new ServerResponseDecoder());
    channelPipeline.addLast("serverRequestDecoder", new ServerRequestDecoder());

    //Reads the responses from the client requests AND
    //reads the inbound requests from the server - Implements channelRead 
    //and exceptionCaught
    channelPipeline.addLast("myResponseHandler", new MyResponseHandler());


}

The problem is that when I flush the response to the server (in MyResponseHandler) and exception is caught in InitialRequestHandler:

ERROR=java.lang.UnsupportedOperationException:unsupported message type: ServerResponse (expected: ByteBuf, FileRegion)

I don't see why the response is not flushed back to the server while the hand shake request is always properly flushed. In both write and flush I have used a ChannelFuture and onOperationComplete this listener f.addListener(ChannelFutureListener.FIRE_EXCEPTION_ON_FAILURE); is fired on failure.

Can I use two handlers in the same pipeline or is it bad practise? Moreover how should I fire an unregister event triggered by user input?

Answer 1

I solved this using one Handler that overrides channelActive and channelRead and I rearranged the encoders and decoders properly. I also solved the "unregister event triggered by user input" this way:

    String line = "line";
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    do {
        logger.info("You typed: " + line + ". Please type 'exit' to terminate the program!");
        line = in.readLine();
    } while (!line.equals("exit"));
    logger.info("You typed: " + line + ". Please wait until the application is successfully shutdown...");

    f.addListener(new ChannelFutureListener() {
        public void operationComplete(ChannelFuture future) throws Exception {
            myChannelPipeline.getMyClientHandler().sendDisconnectRequest(future);
        }
    });

In sendDisconnectReqeust I send the final request and when I get the final response (in channelRead of MyHandler) I call disconnect on the pipeline:

    ChannelPromise cp = new DefaultChannelPromise(ctx.channel());
    ctx.channel().pipeline().disconnect(cp);

However I still have other issues with inbound requests that are never received by my client.