We have upgrade our code that does FTP connections from .NET 2.0 to .NET 4.5. We are seeing that connections when switching to PASSIVE mode are opened in a new session and not the one that made the authentication. So on the firewall we see:
Session 1 - Connection to FTP (port 21)
Session 1 - Authentication (port 21)
Session 1 - Passive mode (port 21)
response come to switch to port 64511 (or some random high port)
Session 2 - Attempt to connect to port 64511
Session 1 is aborted.
On version .NET 2.x the passive connection to the high port was continued on the same session.
Does anybody else sees that, or if it is a true change of the framework?
Thanks.