I'm trying to migrate an old CGI application from an existing Windows 2003 server (IIS 6.0) where it works just fine to a new Windows 2008 server with IIS 7.0 where we're getting the following problem:

After setting up the module handler and everything, I find that I can only access the CGI application (rdbweb.exe) file if I'm calling it via POST request (form submit from another page).

If I just try to type in the URL of the file (issuing a GET request) I get the following error:

HTTP Error 502.2 - Bad Gateway

The specified CGI application misbehaved by not returning a complete set of HTTP headers. The headers it did return are "Exception EInOutError in module rdbweb.exe at 00039B44. I/O error 6. ".

This is a very old application for one of our clients. When we tried to call the vendor they said we need to pay ~ $3000 annual support fee in order to start the talk about it. Of course I'm trying to avoid that!

Note that:

• If we create a normal HTML form that submits to "rdbweb.exe", we get the CGI working normally. We can't use this as workaround though because some pages in the application link to "rdbweb.exe" with normal link not form submit.
• If we run "rdbweb.exe". from a Console (Command Prompt) Window not IIS, we get the normal HTML we'd typically expect, no problem.

We have tried the following:

• Ensuring the CGI module mapped to "rdbweb.exe".in IIS has all permissions (read, write, execute) enabled and also all verbs are allowed not just specific ones, also tried allowing GET, POST explicitely.
• Ensuring the application bool has "enable 32 bit applications" set to true. Ensuring the website runs with an account that has full permissions on the "rdbweb.exe".file and whole website (although we know it "read", "execute" should be enough).
• Ensuring the machine wide IIS setting for "ISAPI and CGI Restrictions" has the full path to "rdbweb.exe".allowed.
• Making sure we have the latest Windows Updates (for IIS6 we found knowledge base articles stating bugs that require hot fixes for IIS6, but nothing similar was found for IIS7).
  • Changing the module from CGI to Fast CGI, not working also

Now the only remaining possibility we have instigated is the following Microsoft Knowledge Base article:http://support.microsoft.com/kb/145661 - Which is about:

CGI Error: The specified CGI application misbehaved by not returning a complete set of HTTP headers. The headers it did return are:

the article suggests the following solution:

Modify the source code for the CGI application header output. The following is an example of a correct header:

 print "HTTP/1.0 200 OK\n";  
 print "Content-Type: text/html\n\n\n";

Unfortunately we do not have the source to try this out, and I'm not sure anyway whether this is the issue we're having.

Can you help me with this problem? Is there a way to make the application work without requiring POST request? Note that on the old IIS6 server the application is working just fine, and I could not find any special IIS configuration that I may want to try its equivalent on IIS7.