Best way to send continuous data in Java using Netty

[Michael.Newcomb at gdc4s.com]

You ChannelConnected ties up the I/O thread forever.

 

 

From: netty-users-bounces at lists.jboss.org
[mailto:netty-users-bounces at lists.jboss.org] On Behalf Of Amit
Phatarphekar
Sent: Friday, July 22, 2011 1:04 PM
To: Netty Users
Subject: Re: Best way to send continuous data in Java using Netty

 

Ok.  I'll let me ask the question a little differently - "How do I send
data to the client continuously?".  


In the code below I'm trying to send localtime every 5 secs to the
client from within channelConnected method.
But it doesn't work for me.  It works only if I comment the while loop.
So if I want to send client time every 5 secs how do i do it?

        public class SRNGServer {

            public static void main(String[] args) throws Exception {
                // Configure the server.
                ServerBootstrap bootstrap = new ServerBootstrap(
                        new NioServerSocketChannelFactory(
                                Executors.newCachedThreadPool(),
                                Executors.newCachedThreadPool()));

                // Configure the pipeline factory.
                bootstrap.setPipelineFactory(new
SRNGServerPipelineFactory());

                // Bind and start to accept incoming connections.
                bootstrap.bind(new InetSocketAddress(8080));
            }
        }



        public class SRNGServerHandler extends
SimpleChannelUpstreamHandler {

            private static final Logger logger = Logger.getLogger(
                    SRNGServerHandler.class.getName());


            @Override
            public void channelConnected(
                    ChannelHandlerContext ctx, ChannelStateEvent e)
throws Exception {
                // Send greeting for a new connection.
              ChannelFuture writeFuture=e.getChannel().write("Welcome to
" + InetAddress.getLocalHost().getHostName() + "!\r\n");


              while(true){
                e.getChannel().write("It is " + new Date() + "
now.\r\n");

                Thread.sleep(1000*5);
              }
            }

            @Override
            public void exceptionCaught(
                    ChannelHandlerContext ctx, ExceptionEvent e) {
                logger.log(
                        Level.WARNING,
                        "Unexpected exception from downstream.",
                        e.getCause());
                e.getChannel().close();
            }
        }



        public class SRNGServerPipelineFactory implements
                ChannelPipelineFactory {

            public ChannelPipeline getPipeline() throws Exception {
                // Create a default pipeline implementation.
                ChannelPipeline pipeline = pipeline();

                pipeline.addLast("encoder", new StringEncoder());
                pipeline.addLast("handler", new SRNGServerHandler());

                return pipeline;
            }
        }



On Fri, Jul 22, 2011 at 2:07 AM, Ioan Eugen Stan <stan.ieugen at gmail.com>
wrote:

2011/7/22 Amit Phatarphekar <amitechforums at gmail.com>:

> I'm planning to use Netty to design a TCP Server.  When the client
connects,
> I have to immediately start pumping
> XML data to the client continuously...for hours/days.  Its that
simple.
>
> So, I override "channelConnected" method and send data from that
method,
> right?...thats great.
>
>
> I will be using the following ChannelFactory
>         ChannelFactory factory =
>             new NioServerSocketChannelFactory(
>                     Executors.newCachedThreadPool(),
>                     Executors.newCachedThreadPool());
>
> NioServerSocketChannelFactory documentation says -> "A worker thread
> performs non-blocking read and write for one or more Channels in a
> non-blocking mode."  Good.
>
> According to effective Java "Item 51: Don't depend on the thread
scheduler",
> I want the worker thread to do a "unit of work" and then
finish/return.
>
> So in my case, though I have to send data continuously, I want to send
some
> chunk (lets say 1 MB ) and then be done (unit of work completed), so
that
> worker thread can return.  Then I'll send another 1 MB.
>
>
> Below example is from the official guide of Netty here ->
> http://docs.jboss.org/netty/3.2/guide/html_single/index.html#d0e440
>
> I guess the question is then, in this scenario, if i had to
unconditionally
> keep sending time to the client, how would I do it, considering
> each send as a unit of work.
>
>
> One way of doing it would be to just put a while loop and do a
> Thread.Sleep.  Any other way?
>
>
>
>         package org.jboss.netty.example.time;
>
>         public class TimeServerHandler extends SimpleChannelHandler {
>
>             @Override
>             public void channelConnected(ChannelHandlerContext ctx,
> ChannelStateEvent e) {1
>                 Channel ch = e.getChannel();
>
>                 ChannelBuffer time = ChannelBuffers.buffer(4);
>                 time.writeInt(System.currentTimeMillis() / 1000);
>
>                 ChannelFuture f = ch.write(time);
>
>                 f.addListener(new ChannelFutureListener() {
>                     public void operationComplete(ChannelFuture
future) {
>                         Channel ch = future.getChannel();
>                         ch.close();
>                     }
>                 });
>             }
>
>             @Override
>             public void exceptionCaught(ChannelHandlerContext ctx,
> ExceptionEvent e) {
>                 e.getCause().printStackTrace();
>                 e.getChannel().close();
>             }
>         }
>
>

> _______________________________________________
> netty-users mailing list
> netty-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/netty-users
>

I didn't understand what exactly is the question, but from what I know
you should have no problems sending data continuously for long periods
of time. And the amount you mentioned is not that large if we are
talking about Ethernet speeds. You should give it a try and see what
happens. If you run into trouble, seek help.

I don't think the sleep is necessary. Reading and writing in Netty is
done when there is data available and when it's room in the buffer.

Hope that helps,
--
Ioan Eugen Stan
http://ieugen.blogspot.com/

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