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<title>GnuTLS 3.4.8: Client with Resume capability example</title>
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<a name="Client-with-Resume-capability-example"></a>
<div class="header">
<p>
Next: <a href="Simple-client-example-with-SRP-authentication.html#Simple-client-example-with-SRP-authentication" accesskey="n" rel="next">Simple client example with SRP authentication</a>, Previous: <a href="Client-using-a-smart-card-with-TLS.html#Client-using-a-smart-card-with-TLS" accesskey="p" rel="prev">Client using a smart card with TLS</a>, Up: <a href="Client-examples.html#Client-examples" accesskey="u" rel="up">Client examples</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="Client-with-resume-capability-example"></a>
<h4 class="subsection">7.1.9 Client with resume capability example</h4>
<a name="ex_002dresume_002dclient"></a>
<p>This is a modification of the simple client example. Here we
demonstrate the use of session resumption. The client tries to connect
once using <acronym>TLS</acronym>, close the connection and then try to
establish a new connection using the previously negotiated data.
</p>
<pre class="verbatim">/* This example code is placed in the public domain. */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
/* Those functions are defined in other examples.
*/
extern void check_alert(gnutls_session_t session, int ret);
extern int tcp_connect(void);
extern void tcp_close(int sd);
#define MAX_BUF 1024
#define CAFILE "/etc/ssl/certs/ca-certificates.crt"
#define MSG "GET / HTTP/1.0\r\n\r\n"
int main(void)
{
int ret;
int sd, ii;
gnutls_session_t session;
char buffer[MAX_BUF + 1];
gnutls_certificate_credentials_t xcred;
/* variables used in session resuming
*/
int t;
char *session_data = NULL;
size_t session_data_size = 0;
gnutls_global_init();
/* X509 stuff */
gnutls_certificate_allocate_credentials(&xcred);
gnutls_certificate_set_x509_trust_file(xcred, CAFILE,
GNUTLS_X509_FMT_PEM);
for (t = 0; t < 2; t++) { /* connect 2 times to the server */
sd = tcp_connect();
gnutls_init(&session, GNUTLS_CLIENT);
gnutls_priority_set_direct(session,
"PERFORMANCE:!ARCFOUR-128",
NULL);
gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE,
xcred);
if (t > 0) {
/* if this is not the first time we connect */
gnutls_session_set_data(session, session_data,
session_data_size);
free(session_data);
}
gnutls_transport_set_int(session, sd);
gnutls_handshake_set_timeout(session,
GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
/* Perform the TLS handshake
*/
do {
ret = gnutls_handshake(session);
}
while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
if (ret < 0) {
fprintf(stderr, "*** Handshake failed\n");
gnutls_perror(ret);
goto end;
} else {
printf("- Handshake was completed\n");
}
if (t == 0) { /* the first time we connect */
/* get the session data size */
gnutls_session_get_data(session, NULL,
&session_data_size);
session_data = malloc(session_data_size);
/* put session data to the session variable */
gnutls_session_get_data(session, session_data,
&session_data_size);
} else { /* the second time we connect */
/* check if we actually resumed the previous session */
if (gnutls_session_is_resumed(session) != 0) {
printf("- Previous session was resumed\n");
} else {
fprintf(stderr,
"*** Previous session was NOT resumed\n");
}
}
/* This function was defined in a previous example
*/
/* print_info(session); */
gnutls_record_send(session, MSG, strlen(MSG));
ret = gnutls_record_recv(session, buffer, MAX_BUF);
if (ret == 0) {
printf("- Peer has closed the TLS connection\n");
goto end;
} else if (ret < 0 && gnutls_error_is_fatal(ret) == 0) {
fprintf(stderr, "*** Warning: %s\n",
gnutls_strerror(ret));
} else if (ret < 0) {
fprintf(stderr, "*** Error: %s\n",
gnutls_strerror(ret));
goto end;
}
if (ret > 0) {
printf("- Received %d bytes: ", ret);
for (ii = 0; ii < ret; ii++) {
fputc(buffer[ii], stdout);
}
fputs("\n", stdout);
}
gnutls_bye(session, GNUTLS_SHUT_RDWR);
end:
tcp_close(sd);
gnutls_deinit(session);
} /* for() */
gnutls_certificate_free_credentials(xcred);
gnutls_global_deinit();
return 0;
}
</pre>
<hr>
<div class="header">
<p>
Next: <a href="Simple-client-example-with-SRP-authentication.html#Simple-client-example-with-SRP-authentication" accesskey="n" rel="next">Simple client example with SRP authentication</a>, Previous: <a href="Client-using-a-smart-card-with-TLS.html#Client-using-a-smart-card-with-TLS" accesskey="p" rel="prev">Client using a smart card with TLS</a>, Up: <a href="Client-examples.html#Client-examples" accesskey="u" rel="up">Client examples</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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