we found bug In C:\Program Files\Analog Devices\VisualDSP 5.0\Blackfin\lib\src\drivers\ethernet\lan9218\lan9218.c
When the driver gets some tcp packets _together_ (one after the other immediately), it handles only the first message and loses the others.
the bug is in the function LAN9218_InterruptHandler:
the old code
new code: use if instead of while
now all the packets are handled correctly and received by the application.