Hi, Inside the BIO structure (struct bio_st), there is a field called num with integer type. It is used to store the file descriptor of the associated socket. Please correct me if I am wrong. I am still investigating what needs to be changed if I plug in my own TCP routines which is implemented in C++ class which does not expose the socket file descriptor. It seems I need to modify the BIO structure to store the TCP class object rather than a simple integer for file descriptor right? Thanks Patrick ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List [EMAIL PROTECTED] Automated List Manager [EMAIL PROTECTED]