Handshake Reads Data From Port


im using your Library on a STM32. Currently i am Trying to establish a FTPS Connection to a Server. All Messages on Port 990 are running well, no problem. But when i connect to the PASV Port, the Function
mbedtls_ssl_handshake reads out the Port Specific Application Data. mbedtls_ssl_read returns a len of Zero. This is strange because on Port 990 everything is working as intended. Anyone got this problem?

HI @sntosauer
You should check the porting to the f_recv callback that is being set in mbedtls_ssl_set_bio().
Is this the same socket that the connection has been established to ?
Mbed TLS support