there is a real difference between oracle 11, 32 bit full client and oracle 12, 32 bit full client.
discovered this when opening files with ArcReader ( ESRI "ArcGIS Published Map" files w/ .pmf extension).
tested both versions (w/ out changing any default settings) of oracle client on the same laptop: when using the full oracle 11, 32 bit client, it goes through our firewall (between 2 buildings) just fine. when using full oracle 12, 32 bit client, the database drops connection somewhere along the way, and doesn't load data in file, UNLESS we use VPN to bypass the firewall. not using a tnsnames file, the connection info is set in the map file. but if i DO set a tnsnames file, i can connect through sqlplus fine using the oracle 12 client.
during testing, we disabled the "SQL ALG" on the firewall, and for a short period completely opened the firewall between these 2 buildings and it made no difference. while working with our networking team and using wireshark, etc, they insist the firewall isn't blocking anything, but our database dropping the connection. but... when using the VPN, it goes through fine...
i suspected it could have something to do with the RECV_BUF_SIZE and SEND_BUF_SIZE but... well it could be that but i didn't have luck when initially trying to change those values on the database server (the services wouldn't start when i used the values in the online documentation).
anyone know what's up? database is oracle 12 c on windows 2012 server. ArcReader 10.3.1.