Code example to write asynchronous server
tommy408
tommytomorow at msn.com
Thu Nov 12 23:44:55 EST 2009
Yanky can I see the MyProtocolEncoder class?
I did this but it doesn't work.
public class MyProtocolEncoder extends StringEncoder{
protected Object encode(
ChannelHandlerContext ctx, Channel channel, Object msg) throws
Exception {
XStream xstream = new XStream();
String xml = xstream.toXML(msg);
return xml;
}
}
yanky wrote:
>
> Hi:
>
> You have a schema in your message. So while encoding and decoding, you
> have
> to recognize a complete request or response message. A common practice is
> to
> use another delimiter that's usually not used in protocol message to mark
> the boundary of different protocol messages. Fortunately, netty do has
> out-of-box support for this problem. You can have a look at example.telnet
> package and also codec.frame package to see how DelimiterBasedFrameDecoder
> can work for you.
>
> Another consideration is that, you have a xml message, of course it is
> string, but you can build your own encoder and decoder to translate POJO
> from/to xml string and then xml string from/to ChannelBuffer. That would
> be
> better. I think it would be like this:
>
> in your PipelineFactory:
>
> // this factory should be used for both client and server to setup
> pipeline
> public ChannelPipeline getPipeline() throws Exception {
> ChannelPipeline pipeline = pipeline();
>
> final int xmlMessageSizeLimit = 8192; // can be modified to meet
> your needs
> // Add the text line codec combination first,
> pipeline.addLast("framer", new DelimiterBasedFrameDecoder(
> xmlMessageSizeLimit, Delimiters.nulDelimiter()));
> pipeline.addLast("decoder", new MyProtocolDecoder());
> pipeline.addLast("encoder", new MyProtocolEncoder());
>
> // and then business logic.
> pipeline.addLast("handler", handler);
> }
>
> and then define your own encoder and decoder:
>
> public class MyProtocolDecoder extends StringDecoder{
> //just override decode method
> protected Object decode(
> ChannelHandlerContext ctx, Channel channel, Object msg) throws
> Exception {
> String xml = super(ctx, channel, msg);
> // then use any xml parser or xml binding tool to map xml to your
> POJO, I use XStream as example
> XStream mapper = new XStream();
> mapper.alias("header", MyProtocolMessage.MyProtocolHeader.class);
> mapper.alias("body", MyProtocolMessage.MyProtocolBody.class);
> MyProtocolMessage protoMsg = mapper.fromXML(xml);
> return protoMsg;
> }
> }
>
> public class MyProtocolMessage {
> MyProtocolHeader header;
> MyProtocolBody body;
>
> static class MyProtocolHeader {......}
> static class MyProtocolBody {......}
>
> }
>
> you should do the reverse process in MyProtocolEncoder
>
> Hope it helps.
>
> good luck
>
> yanky
>
>
> 2009/4/13 manishr22 <manishr22 at gmail.com>
>
>>
>> Hi,
>>
>> How I can read a chunk of data from channel using netty api? my client is
>> writing every time on socket
>>
>> <manish> welcome to the real world</manish>
>>
>> and my netty server needs to read the message till </manish> in one go.
>> and
>> then next message starting from <manish> should be read by Netty server.
>>
>>
>> Any code snippet would be a great help.
>>
>> In my decoder if i read the message from channelbuffer using getbytes()
>> api
>> i see the data but not able to get i can read the whole message in one
>> go. i
>> do see sometime some extra message being read from channel. any reason
>> why
>> it should be.
>>
>>
>>
>> Thanks in advance.
>> Regards
>> Manish
>>
>> Hi Yanky,
>>
>> Thanks so much for your guidance. I will look into factorial example will
>> solving my problem based on this.
>>
>> For any further help, if needed i will post my request here.
>>
>> Thanks again
>>
>> Manish
>>
>>
>>
>> Thanks Yanky for the great answer! So nice that you are here as a
>> part of the community.
>>
>> Cheers,
>>
>> — Trustin Lee, http://gleamynode.net/
>>
>> On Sat, Apr 11, 2009 at 3:16 AM, yanky young <yanky.young at gmail.com>
>> wrote:
>> > Hi:
>> >
>> > I am not netty expert yet. I am just trying to give some hints. In your
>> > case, you are actually building a request/response protocol. And
>> request
>> and
>> > response message may include quite complicated headers and body. So you
>> have
>> > to do some message encoding and decoding in both server side and client
>> > side. You can see in netty codebase there are some out-of-box encoder
>> and
>> > decoder in handler.codec package. I suggest you take a look at
>> > example.fractorial package to see how to implement your own encoder and
>> > decoder for your message format which may be xml. If you are not
>> sensitive
>> > to message format, you can also have a look at example.localtime which
>> use
>> > google protobuf library as real encoder and decoder.
>> >
>> > good luck
>> >
>> > yanky
>> >
>> >
>> >
>> > 2009/4/11 manishr22 <manishr22 at gmail.com>
>> >>
>> >> Hi Yanky,
>> >>
>> >> I took the sample code from svn trunk and saw the codes too. Could you
>> >> please let me know which one among given sample code will fit for the
>> >> reference of my requirement.
>> >>
>> >> Regards,
>> >> Manish
>> >>
>> >> Hi:
>> >>
>> >> Of course there are some sample code in netty project. You can just
>> check
>> >> out the svn trunk and see some samples in example package.
>> >>
>> >> good luck
>> >>
>> >> yanky
>> >>
>> >>
>> >> 2009/4/10 manishr22 <manishr22 at gmail.com>
>> >>
>> >> >
>> >> > Hi,
>> >> >
>> >> > I had a problem statement
>> >> >
>> >> > "to write an asynchronous TCP server to which multiple clients will
>> >> > connect
>> >> > and keep sending messages to my tcp server. My server should read
>> the
>> >> > message and send back some acknowledgment information to the client
>> who
>> >> > sent
>> >> > the data. While reading the data at server since the message comes
>> in
>> >> > particular format i have to do some processing before sending the
>> >> > response
>> >> > back to client."
>> >> >
>> >> > say my client is sending a message structure in which it has some
>> header
>> >> > and then in body it has message like :
>> >> >
>> >> > <manish>welcome to the real world</manish>
>> >> >
>> >> > I was on the way to implement NIO but in between i found such a
>> great
>> >> > library netty and thought of using it. i was trying to make use of
>> this
>> >> > library with the given tutorial and examples but i found that
>> tutorial
>> >> > is
>> >> > not good enough to solve the complex problem.
>> >> >
>> >> > If you can provide me some guidance or sample code that how i should
>> >> > solve
>> >> > my problem using netty library, that would be great.
>> >> >
>> >> > Thanks in advance.
>> >> >
>> >> > Regards
>> >> > Manish
>> >> > --
>> >> > View this message in context:
>> >> >
>> >> >
>> http://n2.nabble.com/Code-example-to-write-asynchronous-server-tp2615889p2615889.html
>> >> > Sent from the Netty User Group mailing list archive at Nabble.com.
>> >> >
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