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<a name="Session-initialization"></a>
<div class="header">
<p>
Next: <a href="Associating-the-credentials.html#Associating-the-credentials" accesskey="n" rel="next">Associating the credentials</a>, Previous: <a href="Preparation.html#Preparation" accesskey="p" rel="prev">Preparation</a>, Up: <a href="How-to-use-GnuTLS-in-applications.html#How-to-use-GnuTLS-in-applications" accesskey="u" rel="up">How to use GnuTLS in applications</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Session-initialization-1"></a>
<h3 class="section">6.3 Session initialization</h3>
<p>In the previous sections we have discussed the global initialization
required for GnuTLS as well as the initialization required for each
authentication method’s credentials (see <a href="Authentication.html#Authentication">Authentication</a>).
In this section we elaborate on the TLS or DTLS session initiation.
Each session is initialized using <a href="Core-TLS-API.html#gnutls_005finit">gnutls_init</a> which among
others is used to specify the type of the connection (server or client),
and the underlying protocol type, i.e., datagram (UDP) or reliable (TCP).
</p>
<dl>
<dt><a name="index-gnutls_005finit"></a>Function: <em>int</em> <strong>gnutls_init</strong> <em>(gnutls_session_t * <var>session</var>, unsigned int <var>flags</var>)</em></dt>
<dd><p><var>session</var>: is a pointer to a <code>gnutls_session_t</code> type.
</p>
<p><var>flags</var>: indicate if this session is to be used for server or client.
</p>
<p>This function initializes the current session to null. Every
session must be initialized before use, so internal structures can
be allocated. This function allocates structures which can only
be free’d by calling <code>gnutls_deinit()</code> . Returns <code>GNUTLS_E_SUCCESS</code> (0) on success.
</p>
<p><code>flags</code> can be one of <code>GNUTLS_CLIENT</code> , <code>GNUTLS_SERVER</code> , <code>GNUTLS_DATAGRAM</code> ,
<code>GNUTLS_NONBLOCK</code> or <code>GNUTLS_NOSIGNAL</code> (since 3.4.2).
</p>
<p>The flag <code>GNUTLS_NO_REPLAY_PROTECTION</code> will disable any
replay protection in DTLS mode. That must only used when
replay protection is achieved using other means.
</p>
<p>Note that since version 3.1.2 this function enables some common
TLS extensions such as session tickets and OCSP certificate status
request in client side by default. To prevent that use the <code>GNUTLS_NO_EXTENSIONS</code>
flag.
</p>
<p><strong>Returns:</strong> <code>GNUTLS_E_SUCCESS</code> on success, or an error code.
</p></dd></dl>
<p>After the session initialization details on the allowed ciphersuites
and protocol versions should be set using the priority functions
such as <a href="Core-TLS-API.html#gnutls_005fpriority_005fset_005fdirect">gnutls_priority_set_direct</a>. We elaborate on them
in <a href="Priority-Strings.html#Priority-Strings">Priority Strings</a>.
The credentials used for the key exchange method, such as certificates
or usernames and passwords should also be associated with the session
current session using <a href="Core-TLS-API.html#gnutls_005fcredentials_005fset">gnutls_credentials_set</a>.
</p>
<dl>
<dt><a name="index-gnutls_005fcredentials_005fset"></a>Function: <em>int</em> <strong>gnutls_credentials_set</strong> <em>(gnutls_session_t <var>session</var>, gnutls_credentials_type_t <var>type</var>, void * <var>cred</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p><var>type</var>: is the type of the credentials
</p>
<p><var>cred</var>: the credentials to set
</p>
<p>Sets the needed credentials for the specified type. Eg username,
password - or public and private keys etc. The <code>cred</code> parameter is
a structure that depends on the specified type and on the current
session (client or server).
</p>
<p>In order to minimize memory usage, and share credentials between
several threads gnutls keeps a pointer to cred, and not the whole
cred structure. Thus you will have to keep the structure allocated
until you call <code>gnutls_deinit()</code> .
</p>
<p>For <code>GNUTLS_CRD_ANON</code> , <code>cred</code> should be
<code>gnutls_anon_client_credentials_t</code> in case of a client. In case of
a server it should be <code>gnutls_anon_server_credentials_t</code> .
</p>
<p>For <code>GNUTLS_CRD_SRP</code> , <code>cred</code> should be <code>gnutls_srp_client_credentials_t</code>
in case of a client, and <code>gnutls_srp_server_credentials_t</code> , in case
of a server.
</p>
<p>For <code>GNUTLS_CRD_CERTIFICATE</code> , <code>cred</code> should be
<code>gnutls_certificate_credentials_t</code> .
</p>
<p><strong>Returns:</strong> On success, <code>GNUTLS_E_SUCCESS</code> (0) is returned,
otherwise a negative error code is returned.
</p></dd></dl>
<hr>
<div class="header">
<p>
Next: <a href="Associating-the-credentials.html#Associating-the-credentials" accesskey="n" rel="next">Associating the credentials</a>, Previous: <a href="Preparation.html#Preparation" accesskey="p" rel="prev">Preparation</a>, Up: <a href="How-to-use-GnuTLS-in-applications.html#How-to-use-GnuTLS-in-applications" accesskey="u" rel="up">How to use GnuTLS in applications</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
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