Differences in SSL and unsecured non-blocking mode

Partial Data: An unsecured socket in non-blocking mode returns the partial data received or written. Since System SSL processes encrypted data, it is not possible to decrypt a message until the entire message is received, making it impossible to return partial data.
Error Indicator: When non-blocking mode is used on a non-secure socket, the status indicator is generally found by checking the errno variable, which is normally EWOULDBLOCK. System SSL does not set the errno variable. Instead the value returned from gsk_secure_socket_read() or gsk_secure_socket_write() is set to GSK_WOULD_BLOCK. gsk_secure_socket_init() returns either GSK_WOULD_BLOCK_READ or GSK_WOULD_BLOCK_WRITE.