Thanks for your kindly help! BIO_get_close() and BIO_set_close() macros are dealing with the "shutdown" field in BIO structure, but there aren't any example or function calling these two functions. Here are the questions, What's the shutdown field meaning? And when is it used? May I treat it as the limit of buffer size? What will happen when the buffer reach that limit? Thx. Mars. ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List [EMAIL PROTECTED] Automated List Manager [EMAIL PROTECTED]