SAP .net Connector 2.0 (NCo) RFC Server in "Running" State but not appearing in SAP

Recently I was involved in upgrading an old component from one SAP server to a different one. It uses SAP Connector 2.0 which is still supported but has it’s end of life in 2013. The PROGID, Gateway Server and Host were changed to point to the new server and the application log showed that the RFC server reported “Running”, but it wasn’t showing up as a registered endpoint in SAP. (Testing the RFC Endpoint also delivered “Program ID not registered.”)

After a lot of thinking, searching and trying many approaches we finally managed to get it going, but since I hadn’t seen this particular case anywhere on Google I must share it.

Turns out that the old server was upgraded from a 6.4 SAP kernel to the 7 series. One of the major changes of this was that librfc32.dll (a library the .Net Connector 2.0 depends on) is not copied to c:\windows\system32 anymore. Since the 6.4 had been installed on the old server the dll was present and this issue never turned up (and so wasn’t documented in the installation documents).

The solution was easy enough to copy librfc32.dll (beware there is also a unicode version librfcu32.dll which we copied just in case aswell) from the SAP directory to c:\windows\system32\ and then the application registered without any hesitation.

Only took 4 hours to find though. I just hope the newer SAP .net Connectors are a bit more debugging friendly and don’t just output “Running” when they are obviously not.