tls setup process paradigm

. 1 , initializes the SSL:
 BOOL the init ( String and certFile, String privFile) {
    SSL_load_error_strings ();
    int r = SSL_library_init ();
    if (r == 0) {
        return false;
    }
    ssl_ctx = SSL_CTX_new (SSLv23_method ());
    if (ssl_ctx == NULL) {
        printf("SSL_library_init failed \n");
        return false;
    }
    err_bio = BIO_new_fd(2, BIO_NOCLOSE);
    r = SSL_CTX_use_certificate_file(ssl_ctx, certFile.c_str(), SSL_FILETYPE_PEM);
    if (r <= 0) {
        printf("SSL_CTX_use_certificate_file %s failed \n", certFile.c_str());
        return false;
    }
    r = SSL_CTX_use_PrivateKey_file(ssl_ctx, privFile.c_str(), SSL_FILETYPE_PEM);
    if (r <= 0) {
        printf("SSL_CTX_use_PrivateKey_file %s failed \n", privFile.c_str());
        return false;
    }
    r = SSL_CTX_check_private_key(ssl_ctx);
    if (r == 0) {
        printf("SSL_CTX_check_private_key failed \n");
        return false;
    }
    printf("SSL inited success\n");
    return true;
}


2 , handshake negotiation:
 int SSLHandshake ()
{
    // Before ssl connection is not established, the reader should be added to the event epoll 
    IF (! Tcp_connected) {
         struct pollfd PFD;
        pfd.fd = fd;
        pfd.events = POLLOUT | POLLERR;
        int r = poll(&pfd, 1, 0);
        if (r == 1 && pfd.revents == POLLOUT) {
            printf("tcp connected fd:%d\n", fd);
            tcp_connected = to true ;
             // Register write event 
            SetEvent (FD_SEND | FD_RECV | FD_CLOSE | FD_ERROR);
        } else {
            printf("poll fd:%d return %d revents %d\n", fd, r, pfd.revents);
            return -1;
        }
    }

    // If ssl is null, initialization using established ssl socket connection 
    IF (ssl == NULL) {
        ssl = SSL_new(ssl_ctx);
        if (ssl == NULL) {
            printf("SSL_new failed, fd:%d \n", fd);
            return -1;
        }

        int r = SSL_set_fd(ssl, fd);
        if (r == 0) {
            printf("SSL_set_fd failed fd:%d \n", fd);
        }
        printf("SSL_set_accept_state for fd:%d \n", fd);
        SSL_set_accept_state(ssl);
    }

    int R & lt = SSL_do_handshake (SSL);
     // if the return value is 1, then the SSL handshake has been completed 
    IF (R & lt == 1 ) {
        ssl_connected = true;
        printf("SSL_do_handshake connected success fd:%d\n", fd);
        return 0;
    }

    // After the handshake process is completed, the corresponding event should be removed 
    int ERR = the SSL_get_error (SSL, R & lt);
     IF (ERR == SSL_ERROR_WANT_WRITE) {
         // remove read event 
        the SetEvent (FD_SEND | FD_CLOSE | FD_ERROR);
        printf("SSL_get_error return want write set events, fd:%d \n", fd);
        return -2;
    } The else  IF (ERR == SSL_ERROR_WANT_READ) {
         // remove the write event 
        SetEvent (FD_RECV | FD_CLOSE | FD_ERROR);
        printf("SSL_get_error return want read set events, fd:%d \n", fd);
        return -2;
    } else {
        printf("SSL_get_error return %d error %d errno %d msg %s fd:%d \n"
                , r, err, errno, strerror(errno), fd);
        return -1;
    }
}