Re: Standalone xPL Hub Summary

[Tom Van den Panhuyzen <tomvdp@xxxxxxxxx>]

I definitely like that last proposal. There is in fact no need for special
packets. When a hub is up an xpl app sending a heartbeat will also receives
that heartbeat (correct ? I suddenly start to doubt...). While an
application is waiting for a hub to appear it can increase its heartbeat
rate.
Tom
On 9/14/05, Gerry Duprey <gerry@xxxxxxx> wrote:
>
> Howdy,
>
> > How about apps *don't* try to bind to 3865 to see if a hub is
there -
> > they don't need to. If we are making a pre-existing hub mandatory
for
> > xPL on a PC, they don't need to check for it's presence.
> >
> > That means the app can't exit immediately when no hub is there
(as it
> > can't tell) - however, this probably makes it a little more
tolerant of
> > start order. It doesn't really matter which service or app starts
first
> > if none of them even *touch* 3865, and they all just assume that
a hub
> > is present.
>
> I could see this, though I can imagine folks who don't know better
> wondering
> why they are app is not running.
>
> The thing that concerns me though is the time it'll take to
"register" the
>
> app with the hub (until hub sees a new client, it won't start
forwarding
> packets to it). If a xPL program only broadcasts it's heartbeat at
startup
>
> and then every 5 minutes there after, it could be 4:59 (worst case)
before
>
> an xPL app that start before the hub starts receiving messages from
the
> hub.
>
> Of course, we could use a slight variation of what Paul suggested in
the
> "ping" stuff. Basically, once the app starts (no polling
port 3865), it
> sends some sort of simple xPL message out every second until it hears
that
>
> message back from itself. When it does, it knows the hub is running
and
> falls back to normal hbeat mode. If it doesn't hear something back in
a
> certain period of time say 30 seconds), it can then determine the hub
was
> not present and tell the user it's missing. It could still keep trying
> after that, just maybe we advise the user there may be something up
after
> a
> 30 seconds.
>
> This would seem to address the race condition, the startup order
> condition,
> the registration time for a later-starting hub and the (eventual)
> detection
> of no hub condition by the app.
>
> Gerry
>
>
> --
> Gerry Duprey
> Ann Arbor, MI 48103
> http://www.cdp1802.org
>
>
> xPL Links: http://www.xplproject.org.uk http://www.xplhal.com
> http://www.xpl.myby.co.uk
> To Post a Message: ukha_xpl@xxxxxxx
> To Subscribe: ukha_xpl-subscribe@xxxxxxx
> To Unsubscribe: ukha_xpl-unsubscribe@xxxxxxx
>
>
>
>  SPONSORED LINKS
>   Protocol analyzer<http://groups.yahoo.com/gads?t=ms&k=Protocol+analyzer&w1=Protocol+analyzer&w2=Sip+protocol&w3=Tcp&w4=Protocol+analysis&w5=Modbus+protocol&w6=Communication+and+networking&c=6&s=128&.sig=-zQy24PvfLhjmPAJIxBRrA>
Sip
> protocol<http://groups.yahoo.com/gads?t=ms&k=Sip+protocol&w1=Protocol+analyzer&w2=Sip+protocol&w3=Tcp&w4=Protocol+analysis&w5=Modbus+protocol&w6=Communication+and+networking&c=6&s=128&.sig=JGLjF9K8NEGOdRT8foIRVg>
> Tcp<http://groups.yahoo.com/gads?t=ms&k=Tcp&w1=Protocol+analyzer&w2=Sip+protocol&w3=Tcp&w4=Protocol+analysis&w5=Modbus+protocol&w6=Communication+and+networking&c=6&s=128&.sig=t3nr9aOH2TXSIeC9jVrLTw>
 Protocol
> analysis<http://groups.yahoo.com/gads?t=ms&k=Protocol+analysis&w1=Protocol+analyzer&w2=Sip+protocol&w3=Tcp&w4=Protocol+analysis&w5=Modbus+protocol&w6=Communication+and+networking&c=6&s=128&.sig=71-6HgIyvQL6snB3ZVnhDQ>
Modbus
> protocol<http://groups.yahoo.com/gads?t=ms&k=Modbus+protocol&w1=Protocol+analyzer&w2=Sip+protocol&w3=Tcp&w4=Protocol+analysis&w5=Modbus+protocol&w6=Communication+and+networking&c=6&s=128&.sig=hp4E4pNsvay8O83dsZNdmA>
Communication
> and networking<http://groups.yahoo.com/gads?t=ms&k=Communication+and+networking&w1=Protocol+analyzer&w2=Sip+protocol&w3=Tcp&w4=Protocol+analysis&w5=Modbus+protocol&w6=Communication+and+networking&c=6&s=128&.sig=ZzBy6FB47RgGz04HtgTmNQ>
>  ------------------------------
> YAHOO! GROUPS LINKS
>
>
>    - Visit your group "ukha_xpl<http://groups.yahoo.com/group/ukha_xpl>"
>    on the web.
>     - To unsubscribe from this group, send an email to:
>   
ukha_xpl-unsubscribe@xxxxxxx<ukha_xpl-unsubscribe@xxxxxxx?subject=Unsubscribe>
>     - Your use of Yahoo! Groups is subject to the Yahoo! Terms of
>    Service <http://docs.yahoo.com/info/terms/>.
>
>
>  ------------------------------
>


[Non-text portions of this message have been removed]