makes sense to me.

What you want is dynamic lan scoped service discovery, rather than
centralised registries for internet scope binding.

I have been prototyping something to do this in my limited spare time; a
multicast IP based system with

-a variant of SLP for locating services. It will use XML, though at the
current stage I just serialize a java object
-an add in to axis that serves up all registered soap services on the
webapp.
-a client to find services by name

There is no central registry at all; things just ask for all implementations
of service:foo and get back a list of URLs; if they set the time to live of
the packet they can ask the lan or the site. If you ask 5 minutes later, you
get back a different list.

I will stick this in the proposal corner of axis in a week or two, under the
name of 'mir': multicast endpoint resolution. I want to get up to using XML
payloads in the datagrams first; serialized objects are quick and dirty for
prototyping but too unstable/unportable.

-steve

----- Original Message -----
From: "Supriyo Chatterjea" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, July 09, 2002 9:44 AM
Subject: Web services on a wireless adhoc network


> Hi,
>
> I'm trying to implement web services on a wireless
> adhoc network. I've given a brief overview of the
> problem and the tools I'm planning to use and that's
> followed by a couple of questions.
>
> Consider a few wireless devices within range of each
> other each providing its own service(s). Each device
> maintains a sort of registry that keeps track of all
> the services that are being offered by all the devices
> in the adhoc network at a certain instant, e.g. if a
> network consists of devices A, B, C and D, device A's
> registry lists the services provided by itself *and*
> the services of devices B, C and D.
>
> If a new device E enters the network, a service
> discovery algorithm ensures that A, B, C, D and E all
> have their own registries updated to indicate the
> services offered by all the devices in the adhoc
> network.

it is not clear you need to do this; the rate of change in a dynamic WLAN
means that you might as well ask for services on demand.

>
> So basically,
>
> (i) every device acts as a service provider *and* a
> service requester (client & server)

OK

>
> (ii) every device has it's own private registry that
> lists its own services *and* the services of the other
> devices in the network

not needed


> Another point is that these services aren't exactly
> services being offered by businesses. It could apply
> to the following scenario, e.g. you receive an email
> on your PDA and would like to print it out. However,
> there isn't any printer available. Some time later,
> you happen to walk into a room where a printer is
> available. Your PDA detects the printer and asks you
> if you would like to print out your email.

not a problem.


> So I'm talking about services like printing,
> displaying some output on a screen, etc., not services
> offered by businesses. And by the way these devices
> are embedded devices.
>
> Now I'm thinking of using Jakarta Tomcat for the web
> server and Apache Axis for the SOAP engine.
>
> Do you think that's an ok choice?


The alternative is Jini, which was designed for this kind of thing.

>
> Does anyone have any idea how I should go about
> implementing the registry?

like I said, what registry? Use multicast or broadcast discovery and you
dont need the central registry


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