Salut,
P J wrote:
> Thank you Jean-Francois ... <http://weblogs.java.net/blog/jfarcand/>
>
> I don't close the connection. AS far as I can see the connection is
> opened once(unless modem power-off or telecomms reset ip's)
>
> By the way, my server is purely passive.. (don't actively open
> connection to modem)
>
> * if it receives a polling message, echo back, if it's a reply match
> with request. The polling message has an id which I then use to
> check whether there are any pending requests - if so, send request.
> * and resume listening,
> * if it receives a polling message, echo back, if it's a reply match
> with request.. rinse lather repeat.
>
This is an interesting application :-). I would think the IP address
combined with the message ID might be a good unique key.
>
> P.s. I'll try and see if ip's can be used in a "best effort" kind of way..
OK let us know the final decision!
A+
-- Jeanfrancois
>
>
> Kind Regards
> Pete
>
>
>
>
> On Tue, Oct 14, 2008 at 6:44 PM, Jeanfrancois Arcand
> <Jeanfrancois.Arcand_at_sun.com <mailto:Jeanfrancois.Arcand_at_sun.com>> wrote:
>
> Salut,
>
>
> P J wrote:
>
> Hello Jeanfrancois,
>
> Thanks for the reply!
>
> Can you elaborate on the above scenario? I would like to
> understand it more...but should the protocol used between the
> server and the modem include a special "header" that describe
> you is sending back the response? Of you might use the IP
> address to detect from which modem the response if from.
>
> Quick question: are you defining the protocol between your
> server and modem, or you already have a text/bytes protocol that
> you can't change?
>
> The protocol is fixed - I can't define/change it :-( (I suppose
> technically a rewrite of firmware could change the protocol,but
> thats not an option now)
>
>
> I agree :-) Pouaaa
>
>
> Elaborate...ok, suppose I send a request to the modem
> $ST+VERSION the reply I get would look something like
> $ST+VERSION=1.13 ..the problem I am experiencing(I can just hear
> grizzly experts rolling around laughing) is that, I need to
> determine from which modem this came. Remember, many similar
> requests might be sent at once, and the replies would be coming
> in at different times, so matching request with response is
> critical.
> Using the IP would be a nice solution, so for testing I tried
> it... the only concern I have is that IPs are volatile - they
> seem to change every so often... what if I sent a request and
> the IP changes? Worst: What if I get a "false" match? That would
> be failure!
>
>
> Thanks for the info. Is your protocol by-directional, e.g. you open
> a connection to the modem, then close the connection OR wait for a
> response? In the latter case, the IP should not change. In the
> former case, then yes inbetween the server->modem and modem->server
> the IP might have changed. In that case I don't see how you can
> found who is calling back without being able to add something to the
> request/response (like a headers/token).
>
> Does it help?
>
> A+
>
> -- Jeanfrancois
>
>
>
>
>
> Welcoming you suggestions
> Kind Regards Pete
>
>
>
>
>
> On Tue, Oct 14, 2008 at 4:38 PM, Jeanfrancois Arcand
> <Jeanfrancois.Arcand_at_sun.com
> <mailto:Jeanfrancois.Arcand_at_sun.com>
> <mailto:Jeanfrancois.Arcand_at_sun.com
> <mailto:Jeanfrancois.Arcand_at_sun.com>>> wrote:
>
> Salut,
>
> sorry for the delay, was on vacation :-)
>
> P J wrote:
>
> RE: My question pertains to the use of the Grizzly Framework
> being used to communicate with hardware devices.
>
> Hello all,
>
> If this is not the correct way to ask questions, please
> direct
> me to the appropriate forum.
>
>
> Quick background:
> * The hardware devices are gprs modems, with embedded
> software(which
> I do not have code access to - so it's a constant)
> These modems
> are programmed to a very simple protocol, and can
> perform a few
> operations.
> * I am tasked to write a central server. The modems
> will poll my
> software, to which I will echo back... on occasion I
> will send
> through an operation request(self test, or parameter
> updates...)
> and of course receive "OKs" back.
> * My server application has to in JAVA.
> * At any point in time I might have to handle hundreds
> or even
> thousands of connections.
> * Using a blog example(Using Grizzly to read TCP
> Packets:
> <http://gallemore.blogspot.com/2007/07/using-grizzly-to-read-tcp-packets.html>http://gallemore.blogspot.com/2007/07/using-grizzly-to-read-tcp-packets.html)
>
>
> <http://gallemore.blogspot.com/2007/07/using-grizzly-to-read-tcp-packets.html>I
> got an echo server running successfully - qualify,
> I'm getting
> polling messages.
>
> <http://gallemore.blogspot.com/2007/07/using-grizzly-to-read-tcp-packets.html>
> * I'm a multiple threads programmer... learning the NIO
> ropes, this
>
> all is a bit different :-)
>
>
> My questions are as follow:
>
> 1. Would Grizzly be an appropriate technology for this
> type of
> application?
>
>
> Yes.
>
> 2. It's so difficult to get relevant documentation.
> Are there any
>
> pdf's, e-books, printed books that would be
> beneficial to read?
>
>
> Take a look at the following entries:
>
>
> http://weblogs.java.net/blog/jfarcand/archive/2008/02/writing_a_tcpud_1.html
>
> https://grizzly.dev.java.net/tutorials/tutorial-framework-filter-sample/index.html
>
>
> 3. I've tried expanding the example to use callbacks.
> (Reason: I
>
> might send a request to a modem 1, and whilst
> waiting for the
> response, need to tend to a polling message from
> modem 2,
> but once
> the reply-results arrive, I need to know that the
> message came
> from modem 1, because the message might not carry an
> identifying
> id - for example, an OK message has no modem ID -
> this of
> course
> is no problem with a 1-to-1 conversation,but with
> thousands
> it's a
> nightmare!) :-(
>
>
> Can you elaborate on the above scenario? I would like to
> understand
> it more...but should the protocol used between the server and the
> modem include a special "header" that describe you is sending
> back
> the response? Of you might use the IP address to detect from
> which
> modem the response if from.
>
> Quick question: are you defining the protocol between your server
> and modem, or you already have a text/bytes protocol that you
> can't
> change?
>
> A+
>
> -- Jeanfrancois
>
>
>
>
> Kind Regards,
> Pete
>
>
>
>
>
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