Hi zhbn,

Have you enabled wolfSSL embedded SSL debug logging?  You can do so by either using the --enable-debug option passed to ./configure, or by defining the DEBUG_WOLFSSL preprocessor define when compiling wolfSSL.  Then, in your application code you can call wolfSSL_Debugging_ON() and wolfSSL_Debugging_OFF() to control wolfSSL debug message logging.

You could also check the return value of either wolfSSL_connect() or wolfSSL_accept(), then in the case of failure (SSL_FAILURE), check the specific error code with wolfSSL_get_error().

Best Regards,
Chris