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Re: [cf-dev] Multiple response to one request
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Ok, I understand that i'm trying to do something that CoAP has not been designed for.
So the empty ACK cannot be handle as it's not consider as a response by the CoapHandler.
Probably a better design would be more suitable in my case (like a monitor status resource created after the accept(), that could be observe by the client).
Thanks Matthias.
Best regards,
Laurent.
/**
* Laurent Lemke
* Doctorant CIFRE - Orange Labs
* Université de Grenoble: équipe ERODS (LIG) & équipe Synchrone (VERIMAG)
*/
----- Mail original -----
De: "Kovatsch Matthias" <kovatsch@xxxxxxxxxxx>
À: "Californium (Cf) developer discussions" <cf-dev@xxxxxxxxxxx>
Envoyé: Lundi 15 Décembre 2014 12:49:11
Objet: Re: [cf-dev] Multiple response to one request
You are still using CoAP in the wrong way... For normal requests there is only a single response. The empty ACK tells the client that the server received the message and that the client can stop retransmitting. The response is then sent separately, preferably in a CON message (NON also possible but in most cases a bad choice). That way, the client will also simply receive the one response...
Ciao
Matthias
> -----Original Message-----
> From: cf-dev-bounces@xxxxxxxxxxx [mailto:cf-dev-bounces@xxxxxxxxxxx] On
> Behalf Of Laurent Lemke
> Sent: Montag, 15. Dezember 2014 01:48
> To: Californium (Cf) developer discussions
> Subject: Re: [cf-dev] Multiple response to one request
>
> Sorry for posting 2 times in a row, but i have investigated the problem.
> With wireshark, I clearly see 2 frames sent from the server to the client: an
> empty ACK + an ACK (or CON depending if i set it).
> The latest is handle by the coap handler, in the asynchronous method
> onLoad.
>
> I made also some other tests with for example sending 2 responses with a
> content simply like that:
>
> @Override
> public void handlePUT(CoapExchange exchange) {
>
> exchange.response(VALID);
> Thread.currentThread().sleep(5000); // removed the try catch clause
> exchange.respond(CHANGED);
> }
>
> Again with wireshark i see those 2 frames.
> But here, it's different: the client handle just the first response and ignore
> the second.
>
> Finally, i tried also with a synchronous client and testing with something like
> that:
> Request request = new Request(Code.PUT); request.setPayload("a");
> request.setURI("coap://localhost:5683/myCoolURI");
> request.send();
> Message firstResp = request.waitForResponse();
> System.out.println(firstRep); Message secondResp =
> request.waitForResponse(); System.out.println(secondResp);
>
> It didn't reach the second print statement.
>
> I guess, the problem is in the client side because the server correctly send
> the coap frame to the client.
>
> Best regards,
> Laurent.
>
> /**
> * Laurent Lemke
> * Doctorant CIFRE - Orange Labs
> * Université de Grenoble: équipe ERODS (LIG) & équipe Synchrone
> (VERIMAG) */
>
> ----- Mail original -----
> De: "Laurent Lemke" <laurent.lemke@xxxxxxx>
> À: "Californium (Cf) developer discussions" <cf-dev@xxxxxxxxxxx>
> Envoyé: Samedi 13 Décembre 2014 18:21:43
> Objet: Re: [cf-dev] Multiple response to one request
>
> Hi Matthias,
>
> Thanks for your answer.
> I understand the meaning of your answer, using a piggybacked response (for
> the first response which correspond to the accept() method in your code <=>
> an ACK response).
> But I'm stuck with the client side where I can read only the second response
> (with the CHANGED ResponseCode in your example).
> It's a very basic sample code inside my onLoad method which consists to print
> some information about the response received (type, token, etc..).
>
> Any idea to handle the 2 responses ?
>
> Thanks,
>
> Best regards,
> Laurent.
>
>
> /**
> * Laurent Lemke
> * Doctorant CIFRE - Orange Labs
> * Université de Grenoble: équipe ERODS (LIG) & équipe Synchrone
> (VERIMAG) */
>
> ----- Mail original -----
> De: "Kovatsch Matthias" <kovatsch@xxxxxxxxxxx>
> À: "Californium (Cf) developer discussions" <cf-dev@xxxxxxxxxxx>
> Envoyé: Samedi 13 Décembre 2014 00:37:36
> Objet: Re: [cf-dev] Multiple response to one request
>
> Hi Laurent
>
> The correct way to do this is using separate responses:
>
> @Override
> public void handlePUT(CoapExchange exchange) {
> // make it a separate response
> exchange.accept();
>
> // your long-lasting task
>
> // finish with the response
> exchange.respond(CHANGED); // reply with response code only
> (shortcut) }
>
> On the client side you can either use an asynchronous request with a
> CoapHandler or you run a synchronous request in a dedicated thread.
>
> Ciao
> Matthias
>
> > -----Original Message-----
> > From: cf-dev-bounces@xxxxxxxxxxx [mailto:cf-dev-bounces@xxxxxxxxxxx]
> > On Behalf Of Laurent Lemke
> > Sent: Freitag, 12. Dezember 2014 21:12
> > To: cf-dev@xxxxxxxxxxx
> > Subject: [cf-dev] Multiple response to one request
> >
> > Hello everybody,
> >
> > I'm currently using californium and I'm trying to have this kind of
> > scenario, a client/server communication :
> > - Client send a request which correspond to an action that take some
> > time (so a POST or PUT, in my case it's a PUT..)
> > - Server send a first response, indicating to the client that he will
> > do the best for doing this action (kind of ACCEPTED code response) ...
> > the action is perform and taking a lot of time ...
> > - Server send a second response indicating that the action has been
> > successfully perform.
> >
> > But well, when i'm trying to do program it with Californium i got stuck.
> > Basically, it seems that a client cannot get multiple response for one
> > request, right ?
> > I mean, i exclude the "observe" property which is not suitable in my case.
> > Because as far as i know, observe rely to the GET verb.. and i'm using
> > a PUT verb here.
> >
> > A possible solution, correct me if i am wrong (or if it's not
> > relevant), would be to have an asynchronous handler that is associated to
> a token ?
> > Because currently, the asynchronous handler handle just one request.
> >
> > Best regards,
> >
> > Laurent Lemke.
> >
> >
> > /**
> > * Laurent Lemke
> > * Doctorant CIFRE - Orange Labs
> > * Université de Grenoble: équipe ERODS (LIG) & équipe Synchrone
> > (VERIMAG) */
> >
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