Question

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.
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) {
            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();
        }
    }

Answer 1

Doing a while/sleep would work, but would not be in the Netty super-scalable style. It would be thread-per-connection programming.

Instead, schedule a periodic job on an Executor that writes a message to the channel.