SOAPpy and callback

[Paul McGuire]

"Diez B. Roggisch" <deets at nospam.web.de> wrote in message 
news:4p94a0Fhr1amU1 at uni-berlin.de...
> fabien.benard at gmail.com schrieb:
>> Hello,
>>
>> I'm trying to find how to use a callback in a SOAP client using SOAPpy.
>> Does SOAPpy have to manage it, or does Python include some API to do
>> it?
>
> I've never seen any callback mentioned in SOAP. Are you sure this is 
> possible with any SOAP implementation, at least standard-wise?
>
> Diez

This is most definitely possible, in fact it is the basis for a new 
asynchronous data collection standard for semiconductor equipment, Interface 
A (replacing the ancient SECS/GEM interface, originally designed to work 
over RS-232).  However, it is a major pain to implement.

As you suggest, you cannot do this from a simple browser or pure SOAP 
client.  To support SOAP callbacks, the client must also itself be a SOAP 
server.  The client sends its own callback server's URL to the primary 
server, and when callbacks are needed, they are sent to that callback URL. 
This really does get quite tricky, though.  For one thing, the vagaries of 
network identification make it unsure whether the URL composed by the client 
for its callback is meaningful/accessible to the server.

In addition, if you are considering implementing this over the untrusted 
internet, you should use SSL authentication both ways (although this further 
complicates your client).

-- Paul