Access to WinCC OA from Webservice via C # API

[juma4]

I have a webservice with which I would like to read data from the WinCC OA. If I now want to access the OaProcessValues, I always get a System.NullReferenceException. Has someone already experiences with the C # API and could give me a tip?
Thanks a lot

[agruber]

Have you followed the complete C# API example? If not try first to create a small program with the complete example code. If that works try to integrate it into your webservice.

Depends on what you want to do you could also query OA via websockets, this should be fairly easy with C#. On OA side there is a websocket server example here:
https://portal.etm.at/index.php?option= ... 16&id=4985

[juma4]

Thanks for the tip. I have created the manager, and it runs. Now I have the .exe as a reference in my webservice integrated. However, I can not access the methods. Do I have to initialize the manager specifically?

[tmalone]

Just FYI, I have been very successful using netGet/netPut/netPost() functions from OA to work with various Web Services. I think I am on my 3rd project with these and never had to build my own API Manager

Todd Malone
USA

[mhargreaves]

Hi Todd

I am trying to use netpost from CONTROL script to submit a post to a webapi server I am hosting.

Do you have any experience with implementing some sort of security on this connection? (Authorization/Authentication)

Mark

[kilianvp]

auth on external Server or WinCC OA?

for netpost on external Server you can use

Authorization: Basic XY

or

Authorization: Bearer XY

[mhargreaves]

Thanks - it is to an external server - a WebApi server that I am creating, so I need to implement the authentication on there.

How to get the 'XY' part in WinCC OA? Can you read the password from the user credentials within WinCC OA?

[kilianvp]

Mark Hargreaves wrote:

Thanks - it is to an external server - a WebApi server that I am creating, so I need to implement the authentication on there.

How to get the 'XY' part in WinCC OA? Can you read the password from the user credentials within WinCC OA?

so you want auth against the external Server with your WinCC OA credentials?

[mhargreaves]

That was the idea I had - I'm not really familiar with authentication methods. If there is a better way of doing it, I would like to learn this.

I need to post some data to my server using netpost from a button click method. This will post to a URL, but I need to protect that URL so that not just anyone can post to it (using a browser etc), but also I don't want the user to have to enter a username and password everytime they click the button.

Any ideas are welcome!

Thanks
Mark

[Gertjan van Schijndel]

Reading the password is not possible.

For preventing access for anyone you can use information, that is already available like sender address or user agent. Or add a custom http header.
But against a hacker it will not really help.