Early data has been received as part of an on-going handshake. This error code can be returned only on server side if and only if early data has been enabled by means of the mbedtls_ssl_conf_early_data() API. This error code can then be returned by mbedtls_ssl_handshake(), mbedtls_ssl_handshake_step(), mbedtls_ssl_read() or mbedtls_ssl_write() if early data has been received as part of the handshake sequence they triggered. To read the early data, call mbedtls_ssl_read_early_data().