gnutls_handshake(3) — Linux manual page


gnutls_handshake(3)              gnutls              gnutls_handshake(3)

NAME         top

       gnutls_handshake - API function

SYNOPSIS         top

       #include <gnutls/gnutls.h>

       int gnutls_handshake(gnutls_session_t session);

ARGUMENTS         top

       gnutls_session_t session
                   is a gnutls_session_t type.

DESCRIPTION         top

       This function performs the handshake of the TLS/SSL protocol, and
       initializes the TLS session parameters.

       The non-fatal errors expected by this function are:
       GNUTLS_E_WARNING_ALERT_RECEIVED. When this function is called for
       re-handshake under TLS 1.2 or earlier, the non-fatal error code
       GNUTLS_E_GOT_APPLICATION_DATA may also be returned.

       The former two interrupt the handshake procedure due to the
       transport layer being interrupted, and the latter because of a
       "warning" alert that was sent by the peer (it is always a good
       idea to check any received alerts). On these non-fatal errors
       call this function again, until it returns 0; cf.
       gnutls_record_get_direction() and gnutls_error_is_fatal(). In
       DTLS sessions the non-fatal error GNUTLS_E_LARGE_PACKET is also
       possible, and indicates that the MTU should be adjusted.

       When this function is called by a server after a rehandshake
       request under TLS 1.2 or earlier the
       GNUTLS_E_GOT_APPLICATION_DATA error code indicates that some data
       were pending prior to peer initiating the handshake.  Under TLS
       1.3 this function when called after a successful handshake, is a
       no-op and always succeeds in server side; in client side this
       function is equivalent to gnutls_session_key_update() with
       GNUTLS_KU_PEER flag.

       This function handles both full and abbreviated TLS handshakes
       (resumption).  For abbreviated handshakes, in client side, the
       gnutls_session_set_data() should be called prior to this function
       to set parameters from a previous session.  In server side,
       resumption is handled by either setting a DB back-end, or setting
       up keys for session tickets.

RETURNS         top

       GNUTLS_E_SUCCESS on a successful handshake, otherwise a negative
       error code.

REPORTING BUGS         top

       Report bugs to <>.
       Home page:

COPYRIGHT         top

       Copyright © 2001- Free Software Foundation, Inc., and others.
       Copying and distribution of this file, with or without
       modification, are permitted in any medium without royalty
       provided the copyright notice and this notice are preserved.

SEE ALSO         top

       The full documentation for gnutls is maintained as a Texinfo
       manual.  If the /usr/share/doc/gnutls/ directory does not contain
       the HTML form visit 

COLOPHON         top

       This page is part of the GnuTLS (GnuTLS Transport Layer Security
       Library) project.  Information about the project can be found at
       ⟨⟩.  If you have a bug report for this
       manual page, send it to  This page was obtained
       from the tarball gnutls-3.7.2.tar.xz fetched from
       ⟨⟩ on 2021-08-27.  If you
       discover any rendering problems in this HTML version of the page,
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       manual page), send a mail to

gnutls                            3.7.2              gnutls_handshake(3)