I'm trying to do a https GET request to my server from Google Sheets sidebar (or dialogue window). That is from a client-side. However, the following error is returned:
If there is any way how to directly communicate with my server's end-point?
P.S. A workaround is to do requests to Google Apps Script, which does UrlFetch and then returns data to the client-side, but this reduces the speed.
Many thanks!