Echo example explaination

[이희승 (Trustin Lee)]

Indeed, this example is too tricky for a beginner to understand.  I
need to separate server-side handler and client-side handler.

Trustin

On Tue, 1 Sep 2009 13:26:57 +0900 (KST)
"J. Mi" <jmi258 at gmail.com> wrote:
> Hi Christian,
> 
> Thanks! I got it. They echo each other just like "wild ping-pong". I
> like that.
> 
> Cheers,
> Jason
> 
> On Mon, Aug 31, 2009 at 8:24 AM, Christian Migowski
> <chrismfwrd at gmail.com>wrote:
> 
> > Hi Jason,
> >
> > i'll try to comment the example, hope it helps:
> >
> > 1. in EchoClient.java line 63 an instance of EchoHandler.java
> > firstMessage is initialized with numbers because the 2nd constructor
> > is used
> > 2. in EchoServer.java an instance of EchoHandler.java firstMessage
> > is initialized as empty (i.e. no data) because the 1st constructor
> > is used
> > 3. in EchoClient.java line 67 the client connects to the server,
> > when this is done, channelConnected() method of EchoHandler is
> > invoked in both the client and the server, but with different
> > processing: 3a) EchoHandler.channelConnected of EchoClient will
> > send firstMessage that is initialized with numbers
> > 3b)  EchoHandler.channelConnected of EchoServer will not send
> > anything because firstMessage is empty (there is nothing to send,
> > even IF write is called)
> > 4. Echohandler.messageReceived of EchoServer is invoked because it
> > received the message from the client, in this method the data
> > received is echoed back to the client
> > 5. now Echohandler.messageReceived of EchoClient is doing the same
> > as the one of EchoServer in 4.) and the wild ping-pong begins until
> > you terminate the program
> >
> > hope this helps,
> > greetings,
> > christian!
> >
> >
> > On Sat, Aug 29, 2009 at 12:54 AM, J. Mi<jmi258 at gmail.com> wrote:
> > > Hi Trustin or any other experienced Netty user,
> > >
> > > I've downloaded Netty 3.1.2. GA and am currently trying to learn
> > > it via
> > your
> > > example of Echo. But I'm having a hard time understanding the
> > > example. I started the server first and seeing a bunch of "0.000
> > > MiB/s" output to
> > the
> > > console.
> > >
> > > I then started the client with the same port (as hard-coded in the
> > server)
> > > of 8080. I then see the output to the console as a bunch "0.0nn
> > > MiB/s"
> > where
> > > nn can be any number.
> > >
> > > I understand that the outout is from the thread ThroughputMonitor.
> > >
> > > I'm not sure if I understand the scenario how things work between
> > > the
> > client
> > > and the server.
> > > The brief description from EchoClient.java is "Sends one message
> > > when a connection is open and echoes back any received data to
> > > the server." The brief description from EchoServer.java is
> > > "Echoes back any received
> > data
> > > from a client."
> > > The EchoHandler.java has the method below:
> > >
> > > public void channelConnected (ChannelHandlerContext ctx,
> > ChannelStateEvent
> > > e) {
> > >
> > > // Send the first message. Server will not send anything here
> > >
> > > // because the firstMessage's capacity is 0.
> > >
> > > e.getChannel().write(
> > >
> > > firstMessage);
> > >
> > > }
> > >
> > > So between the client and the server, who sends a message and who
> > > echoes
> > the
> > > message?
> > > When I added System.out
> > > .println("Message from channelConnected: " +
> > > firstMessage.toString()); in the method, I can see
> > >
> > > Message from channelConnected: BigEndianHeapChannelBuffer(ridx=0,
> > > widx=0, cap=0)
> > >
> > > once when starting EchoClient.
> > >
> > > Could you please explain it to me? This example is a fundamental
> > > one. It should be good starting point for me to understand
> > > Netty's NIO framework.
> > >
> > > If there is a forum some where about this topic and where I
> > > should post
> > any
> > > question like this, please advice as well.
> > >
> > > Thanks in advance
> > > Jason
> > > _______________________________________________
> > > netty-dev mailing list
> > > netty-dev at lists.jboss.org
> > > https://lists.jboss.org/mailman/listinfo/netty-dev
> > >
> > >
> >
> > _______________________________________________
> > netty-dev mailing list
> > netty-dev at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/netty-dev
> >



-- 
Trustin Lee, http://gleamynode.net/