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NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | RETURNS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON |
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gnutls_handshake(3) gnutls gnutls_handshake(3)
gnutls_handshake - API function
#include <gnutls/gnutls.h>
int gnutls_handshake(gnutls_session_t session);
gnutls_session_t session
is a gnutls_session_t type.
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_INTERRUPTED, GNUTLS_E_AGAIN,
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.
GNUTLS_E_SUCCESS on a successful handshake, otherwise a negative
error code.
Report bugs to <[email protected]>.
Home page: https://www.gnutls.org
Copyright © 2001-2023 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.
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
https://www.gnutls.org/manual/
This page is part of the GnuTLS (GnuTLS Transport Layer Security
Library) project. Information about the project can be found at
⟨http://www.gnutls.org/⟩. If you have a bug report for this
manual page, send it to [email protected]. This page was obtained
from the tarball fetched from
⟨https://www.gnupg.org/ftp/gcrypt/gnutls/⟩ on 2025-08-11. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to [email protected]
gnutls 3.8.10 gnutls_handshake(3)