Protocol implementation, Netty socket server, J2ME client

[Trustin Lee]

Hi Nick,

Thank you so much for your contribution to this community first of all, Nick. :)

Would you mind if I ask you to post your example to the wiki?  There
are already a couple interesting example, and I believe yours will
also be a great addition to the list:

  * http://www.jboss.org/community/docs/DOC-13205

With appreciation,

— Trustin Lee, http://gleamynode.net/

On Fri, Apr 10, 2009 at 9:40 PM, Nicholas Clare <nickclare at gmail.com> wrote:
> Hi,
>
>  It doesn't seem like there's a simple example, although it is
> mentioned in the ProtobufDecoder javadocs. I've written a very simple
> example, which I've attached, but I not all that knowledgable of Netty
> (well, not yet). So I hope my example can help, but maybe some more
> experienced readers will be able to give some more advice.
>
> >From what I can see, to use the LengthFieldBasedFrameDecoder, you have
> to layer another decoder on top of it. The
> LengthFieldBasedFrameDecoder just makes sure that the decoder you
> write doesn't have to keep checking if enough data has arrived yet.
> Also, because the LengthFieldBasedFrameDecoder ensures that you get
> just enough data at once, your custom decoder can be based on
> OneToOneDecoder.
>
> I've put all the classes in one file to make it easier to send.
>
> I hope this helps you along,
> Nick
>
> On Fri, Apr 10, 2009 at 1:22 PM, Karasko <karas at uralweb.ru> wrote:
>>
>> Thanks , Nicholas. I'll consider your ideas.
>> Is there some example of LengthFieldBasedFrameDecoder using ? Didn't find it in DOCs.
>>
>>
>> Hi
>>
>> A while ago I wrote server-side code to communicate with a J2ME
>> client. Looking back now, the way I did it was wrong, so here's what
>> I'd recommend for you: I'd use a simple binary protocol, that has a
>> message length field. So a frame could be something like this:
>>
>> len (4 bytes) | message type (1 byte, or more, depending on what you
>> need) | your content
>>
>> You can then use the LengthFieldBasedFrameDecoder class in Netty to do
>> your decoding on the server side. On the client side, it shouldn't be
>> too difficult to read in the length, and then read the rest of the
>> message. You can also make this extensible by having the server or
>> client ignore messages with a type it doesn't understand. So, for
>> example, text messages could be message type 1, pngs message type 2,
>> and so on.
>>
>> As for security, I'm sorry, I'm not too knowledgeable about that, so
>> hopefully someone else can help you. I don't know what J2ME supports
>> in that area, but it might be possible to do some basic encryption.
>>
>> I'm not really an expert, but I hope what I've suggested can maybe help you,
>> Nick
>>
>> On Wed, Apr 8, 2009 at 2:09 PM, Karasko <karas at uralweb.ru> wrote:
>>>
>>> Hi, everyone.
>>> I am writing a sokcet server, using Netty, which would be serve a requests from
>>> J2ME devices (MIDP 2.0, CLDC). I am new person for networking, and concurrent programming,
>>> so any advice or critics is accepted.
>>>
>>> Typical request is to retrieve some data from SQL server, based on text query.
>>>
>>> Response could be a text of various lenght, or sometimes binary data (i.e. PNG image).
>>>
>>> Can you advise some prototype of simple protocol for this, which i can
>>> easily implement on client side J2ME device with standart packages:
>>>
>>> java.io.*;
>>> javax.microedition.io;
>>>
>>> I need protocol to be
>>> 1) extensible (adding new functionality doesn't require to rewrite code everywhere)
>>> 2) compact (less traffic is better)
>>> 3) secure (i don't know how to implement it yet, some advices will be nice)
>>>
>>>
>>> I also want to know how to send an PNG image (or whatever binary data) over socket connection from server..
>>> I think "new line" frame delimiter should be changed for smth else ?
>>>
>>> --
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>>>
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