Structured message reading problem in Netty.

manishr22 manishr22 at gmail.com
Wed Apr 29 07:00:32 EDT 2009 

Hi Trustin,

One small question:

When I am doing the implementation the way you said like adding
ReplayDeocder, if i run whatever be the number of client with number of
messages from each, I see the first message from client read correctly but
from second message the header length and message lengh data read
incorrectly and then application crashes.

Though i tested my application with the use of "DelimiterBasedFrameDecoder"
i see for all client i get correct data. Since the string based delimiter in
serialization and de-serialization from string to byte and then int gives
incorrect result.

So i should be following the approach of ReplayDecoder only but due to above
given problem i am facing issue.

IF first message read correctly it shoudl happen for rest messages too. 

i have tried for @ChannelPipelineCoverage("all") and
@ChannelPipelineCoverage("one") both. but the problem is same.

Any suggestion?

Regards
Manish Ranjan

manishr22 wrote:
> 
> Hi Trustin,
> 
> Thanks for your guidance. This should help me out to solve my problem. You
> people of created a great library, just more of documentation and example
> will help any developer a lot to use Netty.
> 
> Regards
> Manish 
> 
> 
> Trustin Lee-2 wrote:
>> 
>> Hi Manish,
>> 
>> I hope you are not discouraged by previous comment.
>> 
>> I'd like to recommend you to use ReplayingDecoder in this case.
>> 
>>   public class MyDecoder extends ReplayingDecode<VoidEnum> {
>>     @Override
>>     protected Object decode(..., buf, ...) {
>>       int messageLength = buf.readInt();
>>       int headerLength = buf.readInt();
>>       return buf.readBytes(messageLength + headerLength);
>>     }
>>   }
>> 
>> Than the handler placed after 'MyDecoder' will get a ChannelBuffer
>> with expected length.  For example, if a message whose messageLength
>> is 10 and headerLength is 6, you will get a ChannelBuffer whose
>> readable bytes are 4 + 4 + 6 + 10.
>> 
>> Let me know if you have more questions. :)
>> 
>> HTH,
>> 
>> — Trustin Lee, http://gleamynode.net/
>> 
>> On Fri, Apr 24, 2009 at 2:16 PM, manishr22 <manishr22 at gmail.com> wrote:
>>>
>>> Hi Trustin,
>>>
>>> Sorry to bug you guys much.
>>>
>>> I did read the explanation about FrameDecoder and did the earlier
>>> implementation using the same. In my earlier post i gave those source
>>> code
>>> too. Since that was also having problem in buffer's capacity() and
>>> resetReaderIndex().
>>>
>>> I am sorry to give an impression like i wanted to get my code fixed by
>>> someone else, but i never had this intention, i only wanted to get the
>>> advice and opinion from Netty expert, since i was learning this.
>>>
>>> Regards
>>> Manish
>>>
>>> Trustin Lee-2 wrote:
>>>>
>>>> Hi Manish,
>>>>
>>>> Looking from your code, you don't have a FrameDecoder or
>>>> ReplayingDecoder in a pipeline, which means you have a good chance to
>>>> receive only partial data, which leads to IndexOutOfBoundsException.
>>>> Did you have a chance to read the first chapter of the user guide?
>>>> There's good amount of explanation about this issue there.
>>>>
>>>> You and other community members have exchanged quite a lot of
>>>> questions and answers so far.  My impression so far is that you just
>>>> want people to fix your code.  We could solve your problem just by
>>>> writing the fixed code for you, but it would be much better for you to
>>>> follow all the step demonstrated in the user guide.  Then you will
>>>> know what is wrong with your current code very easily.
>>>>
>>>> Also, you might find the factorial example more useful than the
>>>> discard example for your case.
>>>>
>>>> — Trustin Lee, http://gleamynode.net/
>>>>
>>>> On Thu, Apr 23, 2009 at 8:45 PM, manishr22 <manishr22 at gmail.com> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> I am new to netty and tried writing netty-server as per my requirement
>>>>> seeing various examples. But i am not getting the result correctly.
>>>>>
>>>>>
>>>>> I am trying to write a netty server that can read the that will read
>>>>> the
>>>>> message-structre from normal synchronous multi-threaded client ( say
>>>>> 10
>>>>> client is sending 1000 messages each ) to the server.
>>>>>
>>>>>
>>>>> By message structure i mean my client is sending the message in the
>>>>> format :
>>>>>
>>>>>
>>>>> [MESSAGE 1-CLIENT 1]    message-length(first 4 byte) header
>>>>> length(next 4
>>>>> byte) data (including
>>>>>
>>>>> header and body as specified bytes of message length and header
>>>>> length)
>>>>>
>>>>>
>>>>> [MESSAGE 2-CLIENT 1]    message-length(first 4 byte) header
>>>>> length(next 4
>>>>> byte) data (including
>>>>>
>>>>> header and body as specified bytes of message length and header
>>>>> length)
>>>>>
>>>>>
>>>>> ........
>>>>>
>>>>> ........
>>>>>
>>>>> [MESSAGE 1-CLIENT 2]    message-length(first 4 byte) header
>>>>> length(next 4
>>>>> byte) data (including
>>>>>
>>>>> header and body as specified bytes of message length and header
>>>>> length)
>>>>>
>>>>>
>>>>> [MESSAGE 2-CLIENT 2]    message-length(first 4 byte) header
>>>>> length(next 4
>>>>> byte) data (including
>>>>>
>>>>> header and body as specified bytes of message length and header
>>>>> length)
>>>>>
>>>>> ....
>>>>> .....
>>>>>
>>>>> [For N number of client and N
>>>>> http://n2.nabble.com/file/n2682454/netty.zip
>>>>> netty.zip  number of messages]
>>>>>
>>>>> and now my netty server should read all the different messages from
>>>>> client/s
>>>>> and do the proper message parsing and do some business operation.
>>>>>
>>>>>
>>>>> How i can implement the reading of message-structure using netty.
>>>>>
>>>>>
>>>>> I saw several example and implemented something in it. but its not
>>>>> giving
>>>>> the appropriate result rather i am getting exception all the time.
>>>>>
>>>>> The basic source code which i tried for this is also attached for
>>>>> reference.
>>>>>
>>>>> Any suggestion and help with some sample code will be really
>>>>> appreciated.
>>>>>
>>>>>
>>>>> Regards
>>>>>
>>>>> Manish
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> View this message in context:
>>>>> http://n2.nabble.com/Structured-message-reading-problem-in-Netty.-tp2682454p2682454.html
>>>>> Sent from the Netty User Group mailing list archive at Nabble.com.
>>>>>
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>>>>
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> 
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