Newbie questions

[Bozo Juretic]

Ernesto A. wrote:
> Hello,
>
>   
>> 1. What is the best way to implement reconnecting mechanism for TCP
>> client in which the connection with the server should be up at all
>> times. I need to send periodic "ping status" messages to the server as
>> well. At the start of app I need to connect to host (and retry if host
>> is not available), and if the connection goes down I need to reconnect
>> up with the server in some smart way (perhaps you have reconnecting
>> strategies implemented somewhere in netty code?).
>>     
>
> About this first question, I think this part belongs to what in netty
> is called the business logic, or the object in your network framework
> that will take care of handling connections/disconnections, maintain
> session state etc. You should check the javadocs for
> SimpleChannelHandler, this class provides exactly what you need
> through callbacks. There are plenty of examples about how to use it on
> netty's website, I recommend reading the guide first and foremost, so
> you could get in touch with netty principles and get an idea of how
> things fit together.
>
>   
I did reconnects using the IdleStateHandler and bootstrap.connect() in
the main thread. This seems to be a problem, so it seems that the
bootstrap.connect should be run in a separate thread. Thus now I have
this in the main thread:

        Channel channel;
        do {
            logger.info("Connecting to server " + host + ":" + port);
            ChannelFuture f = bootstrap.connect(new
InetSocketAddress(host, port));

            // Wait until the connection attempt succeeds or fails
            f.addListener(new ChannelFutureListener() {

                public void operationComplete(ChannelFuture future) {
                    if (future.isSuccess()) {
                        logger.info("Connected to server");
                        connected = true;
                    } else {
                        logger.info("Connection to server failed: " +
future.getCause().getMessage());
                    }
                }
            });

            try {
                Thread.sleep(15000);
            } catch (InterruptedException ex) {
                logger.warn("interrupted", ex);
            }

        } while (!connected);

This is a problem since there is some other code that needs to be run
afterwards which takes over this thread (JMS consumer.receive()).

I did reconnects of a failed existing connection with IdleStateHandler's
help. Is there a way to put this "first time connect" code (above) in
the handler's channelOpen(), so that it is run by netty, and my main
thread is left to me for my tasks, since I would like to avoid forking
threads on my own (maybe the code will be ported to application server
at some point)?

Also, it the Thread.sleep() a good way to pause execution in netty (i.e.
if I want to wait before I attempt another (re) connect)?

Best regards,

Bozo