Check to see if webservice exists?

[aaa]

What is the most efficient way to do a check to see if a webservice exists
before attempting to execute. I was thinking of just creating an HTTP object
then initiating a request to see if i get a response back from the server.
Is this too much overhead, and how would you imlement this?

[Dan Rogers]

Hi,

There really is no way to do this kind of check. There are so many
possible variables. For instance, someone could have port filtering
enabled, preventing unauthorized calls or unexpected calls from placing
load on a server. Even in an ASP.Net based service, one can disable the
automatic documentation, the WSDL generation, etc, so there is no reliable
way to determine this.

The same holds true for any web based resource. There is no way, other
than trying to access the specific resource, to determine if it is present
at a given moment.

From a best practice perspective, I cannot advise just calling a service to
see if it is alive - because you may not want to make the call at the time
you are checking to see if it is available. A good practice for a service
designer is to create a "checkAvailabil ity" method, and advise all of their
partners that the method is available for determining things such as the
service status, service responsiveness, etc.

In a distributed world, there are no guarantees, so that the designers of
applicaitons that are distrubuted MUST accommodate the possibility of a
given node/service being unavailable.

I hope this helps

Dan Rogers
Microsoft Corporation
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From: "aaa" <aa*@nospam.com >
Subject: Check to see if webservice exists?
Date: Mon, 20 Dec 2004 14:18:04 -0500
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What is the most efficient way to do a check to see if a webservice exists
before attempting to execute. I was thinking of just creating an HTTP object
then initiating a request to see if i get a response back from the server.
Is this too much overhead, and how would you imlement this?