Hi @cqcsdzmt
As mentioned in this anouncement, Mbed TLS is now maintained under open governance at TrustedFirmware.org.
I would suggest you post your question there, as it doesn’t seem your question is Pelion related.
At a glance, the error -0x7280 means: `-0x7280 - SSL - The connection indicated an EOF" . Since this was received after your client sent the Client hello message, I would say that the server can’t establish a successful TLS handshake with the parameters given in your client hello. Most likely no matching ciphersuite, and it is probably a configuration issue.
Regards,
mbed Support
Ron