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From Shaun Williams <shaun_willi...@apple.com>
Subject Re: Writing Unsolicited Messages to a Connected Netty Client
Date Fri, 20 Jan 2012 17:25:52 GMT
Another solution is to use the response leg of a transaction to push messages to the client,
e.g. provide a server protocol like this:

WeatherUpdate listenForUpdate();

This would essentially block until an update is available.  The only problem is that if the
client is expecting a series of updates, it would need to call this method again after receiving
each update.

This is not an ideal solution, but it might solve your problem.

-Shaun


On Jan 20, 2012, at 8:24 AM, Armin Garcia wrote:

> Hi James,
>  
> First, thank you for your response.
>  
> Yes, you are right.  I am trying to setup a bi-directional communication link.  Your
suggestion would definitely accomplish this requirement.  I was hoping the same channel could
be reused without having to establish another uni-directional link.  Netty or rather NIO is
inherently bi-directional.  I am suspecting RPC by definition is only uni-directional or rather
a pull technology?
>  
> One of my goals is to support as many different language bindings using Avro.  PHP is
one of those languages.  Unfortunately, the PHP library can only function as a client.
>  
>                -Armin
> 
> On Fri, Jan 20, 2012 at 7:47 AM, James Baldassari <jbaldassari@gmail.com> wrote:
> Hi Armin,
> 
> Could you explain a little more about what you're trying to do?  It sounds like you want
a protocol in which either client or the server initiates a remote procedure call.  The easiest
way to do this is to have the client also be a server and the server also be a client.  For
example, consider the following protocols:
> 
> protocol WeatherClient {
>   double getTemperature(string postalCode);
>   void registerForTemperatureUpdates(string postalCode, string clientHost, int clientPort);
> }
> 
> protocol WeatherUpdateListener {
>   void onTemperatureUpdate(String postalCode, double newTemperature);
> }
> 
> The client side would use WeatherClient (and SpecificRequestor/NettyTransceiver) to request
the temperature for some postal code from the server.  The client could also register with
the server for temperature updates by passing the postal code it's interested in as well as
the hostname/IP and port of a netty server running on the client.  The client would run its
own netty server using a WeatherUpdateListener and SpecificResponder.  When the server has
a temperature update to send back to the client, it would send a message to the client using
the WeatherUpdateListener interface.  Is this close to what you're looking for?
> 
> -James
> 
> 
> 
> On Fri, Jan 20, 2012 at 6:34 AM, Armin Garcia <armin.garcia@arrayent.com> wrote:
> I am trying to figure out how a message can be sent through a Netty Server to a connected
client.  I see the channel is stored in a group for each client that connects to a Netty Server:
> 
> public void channelOpen(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception
> {
>      e.getChannel().write(null);
>      allChannels.add(e.getChannel());
>      super.channelOpen(ctx, e);
> }
> 
> The challenge is how to leverage this channel in order to send an unsolicited message
to the client.  Is there an example that writes to the channel but not as a response to a
message received?  
> 
> I fully expect to take the existing Netty Server and modify it.  I suspect the solution
lies somewhere in creating a NettyDataPack then writing it to the channel.  I'm definitely
an Avro  greenhorn, so I'm a bit unsure of how to wrangle my message into a NettyDataPack.
> 
>            -Armin 
> 
> 
> 
> 


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