WebSocketClientHandler : how to wait for server response without closing channel ?

[philippe...@gmail.com]

Hello,

I am working with Websocket on client side with Netty.
I have a use case where I need to wait on the client side for server response and timeout if answer does not come in a defined interval.

I have looked at https://github.com/netty/netty/blob/master/example/src/main/java/io/netty/example/http/websocketx/client/ code comment and there is something not clear for me:
Comment says:
// Send 10 messages and wait for responses
ch.write(new TextWebSocketFrame("Message #" + i));

But  it seems it is the following code that makes the client wait for server response:
ch.closeFuture().sync();

Note that in my case I don't want to close the websocket as shown in sample.

So my idea to implement this was to use a CountDownLatch which I would pass to WebSocketClientHandler.
In the equivalent of WebSocketClient, I would wait on latch with timeout.

If WebSocketClientHandler gets a response it would decrement latch and make WebSocketClient continue processing, otherwise timeout would occur.

Is this way of doing it is correct ? Are there better way to do it ?

Thanks for your help
Regards
Philippe

[Norman Maurer]

You need to have a ChannelInboundHandler in your ChannelPipeline which will intercept the received frames and so handle them. For timeout you could use the IdleStateHandler.

Bye,

Norman

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[philippe...@gmail.com]

Hello ,
Thanks for rapid answer.
Thanks Norman, for timeout it's ok, I had found info in one of your previous answers.

But for blocking client after sending , it is not clear for me.
As I want to block the thread just after this (in your example of WebSocketClient:

            System.out.println("WebSocket Client sending message");
            for (int i = 0; i < 10; i++) {

                ch.write(new TextWebSocketFrame("Message #" + i));
            }

wait here a certain time for server response.

I may misunderstand but the channelinboundhandler is executed by another thread right ?

thanks

Regards

[Norman Maurer]

If you really want to block you could make use of a CountDownLatch which is injected in the ChannelHandler. But I would advice to rethink your usage of Netty as most of the times you don't want to block to get most out of your application

Am 23.06.2013 um 10:49 schrieb philippe...@gmail.com:

> Hello ,
> Thanks for rapid answer.
> Thanks Norman, for timeout it's ok, I had found info in one of your previous answers.
>
> But for blocking client after sending , it is not clear for me.
> As I want to block the thread just after this (in your example of WebSocketClient:
>
> System.out.println("WebSocket Client sending message");
> for (int i = 0; i < 10; i++) {

> ch.write(new TextWebSocketFrame("Message #" + i));
> }

> wait here a certain time for server response.
>
> I may misunderstand but the channelinboundhandler is executed by another thread right ?
>
> thanks
>
> Regards
>

[philippe...@gmail.com]

Hello Norman,
Thanks for answer.

Regards
Philippe