Calling Web Service from VB6

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lozd - 11 May 2005 12:26 GMT

Hi,

I'm building a web service for a client and would like to know if it's
possible to achieve it the way they'd like it.

Basically I need to call a dotnet web service from a client application
written in VB6 and (if possible) avoid packaging a dotnet component with this
VB6 application.

The client wants the client app used on sales machines which don't have the
dotnet framework installed and wants to avoid installing it on these machines.

Is it possible to call a Web Service directly from VB6?

Alternatively could I create a COM wrapper class with dotnet in a central
location (i.e. a machine with dotnet installed on it) on their network and
then reference that wrapper class from the various client machine's VB6 app?

Any help/pointers would be appreciated.

Thanks.

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Chad Z. Hower aka Kudzu - 11 May 2005 17:03 GMT

> Basically I need to call a dotnet web service from a client application
> written in VB6 and (if possible) avoid packaging a dotnet component with
> this VB6 application.

Its possible, but its a LOT more difficult because VB6 AFAIK doesnt have
native webservice support. Interpreting WSDL is not a trivial task.

> Is it possible to call a Web Service directly from VB6?

Yes. But the question should be "how hard is it"? A lot also depends on the
complexity of the webservice you want to call. Simple ones can be easily hand
hacked with HTTP.

> Alternatively could I create a COM wrapper class with dotnet in a
> central location (i.e. a machine with dotnet installed on it) on their
> network and then reference that wrapper class from the various client
> machine's VB6 app?

Using DCOM yes, but I wouldnt recommend it. Thats just another weak link that
will get broken.

Why not just install .NET framework? The users will never even notice.

--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programming is an art form that fights back"

Blog: http://blogs.atozed.com/kudzu

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lozd - 11 May 2005 18:04 GMT

Thanks for the response.

> Why not just install .NET framework? The users will never even notice.

If it were my choice I'd be doing this but unfortunately people higher up
won't allow this without a fair bit of reviewing, etc.

The webservice isn't too complex, basically providing a set of details to
the webservice to be written to a DB at the webservices end and waiting on a
boolean response. Since there could be a large number of fields being sent
I'm guessing hand-hacking with HTTP would be quite awkward.

The problem is the details are collected in a large VB6 app (which is
installed and used over most of the network) so I need some way to present
them to the webservice.

I'll try pushing for installing the .NET framework on a wider basis but
failing that I think I'll be forced to try the DCOM approach :-(

Thanks for the clarification, I appreciate it a lot.

> > Basically I need to call a dotnet web service from a client application
> > written in VB6 and (if possible) avoid packaging a dotnet component with
[quoted text clipped - 24 lines]
>
> Blog: http://blogs.atozed.com/kudzu

Reply to this Message

Chad Z. Hower aka Kudzu - 11 May 2005 18:15 GMT

> The webservice isn't too complex, basically providing a set of details
> to the webservice to be written to a DB at the webservices end and
> waiting on a boolean response. Since there could be a large number of
> fields being sent I'm guessing hand-hacking with HTTP would be quite
> awkward.

Sending is easy, its the response that proves more difficult. If its return
value is simple, you can easily use a soap spy and look at whats submitted.
Cosntruct a string with the same, and POST it. Get response, extract. Pretty
easy - and use a C#/VB.NET client to make the initial go.

For HTTP post you might consider Indy, its free:
http://www.indyproject.org/

--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programming is an art form that fights back"

Blog: http://blogs.atozed.com/kudzu

Reply to this Message

lozd - 11 May 2005 19:26 GMT

Thanks a lot, I'll give that a try. Aside from my two thoughts (calling from
VB6 directly or using a central COM wrapper) I was short on ideas.

Cheers, you've been more than helpful!

> > The webservice isn't too complex, basically providing a set of details
> > to the webservice to be written to a DB at the webservices end and
[quoted text clipped - 15 lines]
>
> Blog: http://blogs.atozed.com/kudzu

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Calling Web Service from VB6

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