I have set up an Nginx as a front end to manage secure connection and authorization for the Radicale calendar server which I use to synch my Lightning calendar on my desktop, laptop and Android phone (it uses the Caldav Synch app). It all works fine after a long and steep learning curve for me at least. One strange thing I have noticed is that I keep getting an error in the Nginx error log for the Android device, here are the abbreviated logs from Nginx's access.log and error.log:

access.log entries:
199.7.156.144 - - [20/Oct/2013:15:38:49 -0400] "OPTIONS /USERID/testcalhttps/ HTTP/1.1" 401 194 "-" "CalDAV-Sync (Android) (like iOS/5.0.1 (9A405) dataaccessd/1.0) gzip" "-"

199.1.1.1 - MYUSERID [20/Oct/2013:15:38:50 -0400] "OPTIONS /USERID/testcalhttps/ HTTP/1.1" 200 5 "-" "CalDAV-Sync (Android) (like iOS/5.0.1 (9A405) dataaccessd/1.0) gzip" "-"

199.1.1.1 - MYUSERID [20/Oct/2013:15:38:50 -0400] "PROPFIND /USERID/testcalhttps/ HTTP/1.1" 207 1646 "-" "CalDAV-Sync (Android) (like iOS/5.0.1 (9A405) dataaccessd/1.0) gzip" "-"

199.1.1.1 - MYUSERID [20/Oct/2013:15:38:51 -0400] "REPORT /USERID/testcalhttps/ HTTP/1.1" 207 8525 "-" "CalDAV-Sync (Android) (like iOS/5.0.1 (9A405) dataaccessd/1.0) gzip" "-"

199.1.1.1 - MYUSERID [20/Oct/2013:15:38:53 -0400] "PUT /USERID/testcalhttps/e024b939-a58c-4b42-8f65-77d75942541c.ics HTTP/1.1" 201 5 "-" "CalDAV-Sync (Android) (like iOS/5.0.1 (9A405) dataaccessd/1.0) gzip" "-"

error.log entries:
2013/10/20 15:38:49 [error] 6797#0: *241 no user/password was provided for basic authentication, client: 199.1.1.1, server: , request: "OPTIONS /USERID/testcalhttps/ HTTP/1.1", host: "mysserver.com:1905"

The userid and password were correctly entered during setup of the calendar on the client and as I said it all works fine... I can add, delete, modify calendar entries and synch across all my devices. But I keep getting this pesky error when using my phone.

I noticed that in the access.log the first access corresponds to the error message in the error log.... and then there are four more access messages with my USERID appended to the IP address. So it looks like the userid/password are processed after the first request somehow. Also, it may be helpful to know that the phone is connecting to Nginx via the internet and portforwarding via my router to the server. Might this error message simply be the result of the way I am accessing the server... as I don't get the same error when I access the server via the LAN and my laptop.

Thanks in advance!

Joseph