Re: Callbacks in SOAP

[rd...@harlequin.co.uk]

At 4/30/2001 7:44:41 PM, Wouter Cloetens <wo...@mind.be> wrote:
#  And how exactly would a Microsoft WebServices server call an applet, running
#  in a browser behind a firewall that will not let any incoming connection
#  through?

I'm only really concerned with intranets. Although it occurs to me that the
browser indulges in two-way communication, and I -thought- SOAP/XML-RPC worked
over http (I could be well mistaken here). I digress. Below is a quote from the
MSDN network. I'd be interested to know -how- they achieve callbacks.

<URL:http://msdn.microsoft.com/workshop/author/webservice/using.asp>

<quote>
Calling Methods on Web Services
Once the behavior has been attached to the document and the friendly name for at
least one WebService has been defined, the call method can be used to invoke
methods.

Due to the stateless nature of HTTP, the WebService behavior communicates with
Web Services asynchronously. In many cases, it is necessary to identify each
call to the Web Service uniquely, as each call made to a given method might
return a different result. The call method returns a unique value so that the
returned result can be identified with a specific instance of a method call.
Here's the basic syntax for call.

iCallID = id.FriendlyName.call([CallbackHandler,] "MethodName",  Param1, Param2,
 ...);
The call method has an optional first parameter that specifies a callback
handler function to process the results received from the method call. If no
callback handler is specified, then the event handler for the onresult event is
used. The onresult event is fired by the WebService behavior once the result of
the remote call has completed. Both approaches are explained in Handling Results
 from WebService Calls.

Continuing with the sample, the following approach can be used to return a
unique value from a call to a Web Service method named add.

<script language="JavaScript">
var iCallID;
iCallID = service.MyMath.call("add",5,6);
</script>

</quote>

#  Note that callbacks are not a SOAP issue, of course. Plenty of transport
#  mechanisms can relay peer-to-peer messages (rather than the client/server
#  paradigm that's typical of the v1/v2 design of Apache-SOAP, but not the
#  v3 a.k.a. Axis design).

Are you saying here that callbacks are possible with web services running under
an Apache paradigm?

Roger



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