ODP.net managed driver throws ORA-12570: Network Session: Unexpected packet read error
After opening a ticket with the Oracle support, they sent an unofficial updated version of the managed ODP.net library which seems to fix the issue.
Hopefully the fix should be part of the next ODAC release (the latest available today is from Oct 2015).
If you see this error in your application, it's probably due to the same bug in the managed ODP.net library, not the way you use it.
Another thing to consider is if something in the network infrastructure could interrupt idle tcp/ip connections during the execution of long requests as described in this SO answer.