I have a asmx-webservice. When I try to access it by using the URL directly, I get an error "Requested Format Unrecognized" (I hope the translation is correct; I have a Dutch version). When I try to make a service reference, I get the following error: There was an error downloading 'http://bliep.hulppeldepup.nl/bliep.asmx/_vti_bin/ListData.svc/$metadata'.
The request failed with HTTP status 405: Method Not Allowed.

After some googling, I got to this page https://support.microsoft.com/en-us/kb/330221/nl that tells me that I have to adjust settingsin the firewall to remove unknown headers. Unfortunately it doesn't tell me how, and I can't find the answer anywhere.

The strange thing is, that on the same site I have another asmx webservice that I access through AJAX, without problems. Now I want to do the same thing with a Windows Forms application, and problems arrise.

How can I make my asmx webservice available for my program?