I have developed an app that I have been running for 2 years on FilemakerGo. It runs independently - then backs-up on a filmmaker server (now FilemakerCloud). It opens fmnet:/ip/file as external file source. Running in FilemakerGo on an iPhone - it works fine - can update and backup files - but when run via SDK on simulator or on iPhone - it cannot connect. No specific warnings.
I have tried a number of variations - without success. Cannot find anything similar in from or web searches!