programs/ssl/dtls_server.c - mirror/mbed-tls - TrustedFirmware Git Browser

 /*
  *  Simple DTLS server demonstration program
  *
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */

 #include "mbedtls/build_info.h"

 #include "mbedtls/platform.h"

 /* Uncomment out the following line to default to IPv4 and disable IPv6 */
 //#define FORCE_IPV4

 #ifdef FORCE_IPV4
 #define BIND_IP     "0.0.0.0"     /* Forces IPv4 */
 #else
 #define BIND_IP     "::"
 #endif

 #if !defined(MBEDTLS_SSL_SRV_C) || !defined(MBEDTLS_SSL_PROTO_DTLS) ||    \
     !defined(MBEDTLS_SSL_COOKIE_C) || !defined(MBEDTLS_NET_C) ||          \
     !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C) ||        \
     !defined(MBEDTLS_X509_CRT_PARSE_C) || !defined(MBEDTLS_RSA_C) ||      \
     !defined(MBEDTLS_PEM_PARSE_C) || !defined(MBEDTLS_TIMING_C)

 int main( void )
 {
     printf( "MBEDTLS_SSL_SRV_C and/or MBEDTLS_SSL_PROTO_DTLS and/or "
             "MBEDTLS_SSL_COOKIE_C and/or MBEDTLS_NET_C and/or "
             "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C and/or "
             "MBEDTLS_X509_CRT_PARSE_C and/or MBEDTLS_RSA_C and/or "
             "MBEDTLS_PEM_PARSE_C and/or MBEDTLS_TIMING_C not defined.\n" );
     mbedtls_exit( 0 );
 }
 #else

 #if defined(_WIN32)
 #include <windows.h>
 #endif

 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>

 #include "mbedtls/entropy.h"
 #include "mbedtls/ctr_drbg.h"
 #include "mbedtls/x509.h"
 #include "mbedtls/ssl.h"
 #include "mbedtls/ssl_cookie.h"
 #include "mbedtls/net_sockets.h"
 #include "mbedtls/error.h"
 #include "mbedtls/debug.h"
 #include "mbedtls/timing.h"

 #include "test/certs.h"

 #if defined(MBEDTLS_SSL_CACHE_C)
 #include "mbedtls/ssl_cache.h"
 #endif

 #define READ_TIMEOUT_MS 10000   /* 10 seconds */
 #define DEBUG_LEVEL 0


 static void my_debug( void *ctx, int level,
                       const char *file, int line,
                       const char *str )
 {
     ((void) level);

     mbedtls_fprintf( (FILE *) ctx, "%s:%04d: %s", file, line, str );
     fflush(  (FILE *) ctx  );
 }

 int main( void )
 {
     int ret, len;
     mbedtls_net_context listen_fd, client_fd;
     unsigned char buf[1024];
     const char *pers = "dtls_server";
     unsigned char client_ip[16] = { 0 };
     size_t cliip_len;
     mbedtls_ssl_cookie_ctx cookie_ctx;

     mbedtls_entropy_context entropy;
     mbedtls_ctr_drbg_context ctr_drbg;
     mbedtls_ssl_context ssl;
     mbedtls_ssl_config conf;
     mbedtls_x509_crt srvcert;
     mbedtls_pk_context pkey;
     mbedtls_timing_delay_context timer;
 #if defined(MBEDTLS_SSL_CACHE_C)
     mbedtls_ssl_cache_context cache;
 #endif

     mbedtls_net_init( &listen_fd );
     mbedtls_net_init( &client_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     mbedtls_ssl_cookie_init( &cookie_ctx );
 #if defined(MBEDTLS_SSL_CACHE_C)
     mbedtls_ssl_cache_init( &cache );
 #endif
     mbedtls_x509_crt_init( &srvcert );
     mbedtls_pk_init( &pkey );
     mbedtls_entropy_init( &entropy );
     mbedtls_ctr_drbg_init( &ctr_drbg );

 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_debug_set_threshold( DEBUG_LEVEL );
 #endif

     /*
      * 1. Seed the RNG
      */
     printf( "  . Seeding the random number generator..." );
     fflush( stdout );

     if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
                                (const unsigned char *) pers,
                                strlen( pers ) ) ) != 0 )
     {
         printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
         goto exit;
     }

     printf( " ok\n" );

     /*
      * 2. Load the certificates and private RSA key
      */
     printf( "\n  . Loading the server cert. and key..." );
     fflush( stdout );

     /*
      * This demonstration program uses embedded test certificates.
      * Instead, you may want to use mbedtls_x509_crt_parse_file() to read the
      * server and CA certificates, as well as mbedtls_pk_parse_keyfile().
      */
     ret = mbedtls_x509_crt_parse( &srvcert, (const unsigned char *) mbedtls_test_srv_crt,
                           mbedtls_test_srv_crt_len );
     if( ret != 0 )
     {
         printf( " failed\n  !  mbedtls_x509_crt_parse returned %d\n\n", ret );
         goto exit;
     }

     ret = mbedtls_x509_crt_parse( &srvcert, (const unsigned char *) mbedtls_test_cas_pem,
                           mbedtls_test_cas_pem_len );
     if( ret != 0 )
     {
         printf( " failed\n  !  mbedtls_x509_crt_parse returned %d\n\n", ret );
         goto exit;
     }

     ret =  mbedtls_pk_parse_key( &pkey, (const unsigned char *) mbedtls_test_srv_key,
                          mbedtls_test_srv_key_len, NULL, 0, mbedtls_ctr_drbg_random, &ctr_drbg );
     if( ret != 0 )
     {
         printf( " failed\n  !  mbedtls_pk_parse_key returned %d\n\n", ret );
         goto exit;
     }

     printf( " ok\n" );

     /*
      * 3. Setup the "listening" UDP socket
      */
     printf( "  . Bind on udp/*/4433 ..." );
     fflush( stdout );

     if( ( ret = mbedtls_net_bind( &listen_fd, BIND_IP, "4433", MBEDTLS_NET_PROTO_UDP ) ) != 0 )
     {
         printf( " failed\n  ! mbedtls_net_bind returned %d\n\n", ret );
         goto exit;
     }

     printf( " ok\n" );

     /*
      * 4. Setup stuff
      */
     printf( "  . Setting up the DTLS data..." );
     fflush( stdout );

     if( ( ret = mbedtls_ssl_config_defaults( &conf,
                     MBEDTLS_SSL_IS_SERVER,
                     MBEDTLS_SSL_TRANSPORT_DATAGRAM,
                     MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
         goto exit;
     }

     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
     mbedtls_ssl_conf_read_timeout( &conf, READ_TIMEOUT_MS );

 #if defined(MBEDTLS_SSL_CACHE_C)
     mbedtls_ssl_conf_session_cache( &conf, &cache,
                                    mbedtls_ssl_cache_get,
                                    mbedtls_ssl_cache_set );
 #endif

     mbedtls_ssl_conf_ca_chain( &conf, srvcert.next, NULL );
    if( ( ret = mbedtls_ssl_conf_own_cert( &conf, &srvcert, &pkey ) ) != 0 )
     {
         printf( " failed\n  ! mbedtls_ssl_conf_own_cert returned %d\n\n", ret );
         goto exit;
     }

     if( ( ret = mbedtls_ssl_cookie_setup( &cookie_ctx,
                                   mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
         printf( " failed\n  ! mbedtls_ssl_cookie_setup returned %d\n\n", ret );
         goto exit;
     }

     mbedtls_ssl_conf_dtls_cookies( &conf, mbedtls_ssl_cookie_write, mbedtls_ssl_cookie_check,
                                &cookie_ctx );

     if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
     {
         printf( " failed\n  ! mbedtls_ssl_setup returned %d\n\n", ret );
         goto exit;
     }

     mbedtls_ssl_set_timer_cb( &ssl, &timer, mbedtls_timing_set_delay,
                                             mbedtls_timing_get_delay );

     printf( " ok\n" );

 reset:
 #ifdef MBEDTLS_ERROR_C
     if( ret != 0 )
     {
         char error_buf[100];
         mbedtls_strerror( ret, error_buf, 100 );
         printf("Last error was: %d - %s\n\n", ret, error_buf );
     }
 #endif

     mbedtls_net_free( &client_fd );

     mbedtls_ssl_session_reset( &ssl );

     /*
      * 3. Wait until a client connects
      */
     printf( "  . Waiting for a remote connection ..." );
     fflush( stdout );

     if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
                     client_ip, sizeof( client_ip ), &cliip_len ) ) != 0 )
     {
         printf( " failed\n  ! mbedtls_net_accept returned %d\n\n", ret );
         goto exit;
     }

     /* For HelloVerifyRequest cookies */
     if( ( ret = mbedtls_ssl_set_client_transport_id( &ssl,
                     client_ip, cliip_len ) ) != 0 )
     {
         printf( " failed\n  ! "
                 "mbedtls_ssl_set_client_transport_id() returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }

     mbedtls_ssl_set_bio( &ssl, &client_fd,
                          mbedtls_net_send, mbedtls_net_recv, mbedtls_net_recv_timeout );

     printf( " ok\n" );

     /*
      * 5. Handshake
      */
     printf( "  . Performing the DTLS handshake..." );
     fflush( stdout );

     do ret = mbedtls_ssl_handshake( &ssl );
     while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
            ret == MBEDTLS_ERR_SSL_WANT_WRITE );

     if( ret == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED )
     {
         printf( " hello verification requested\n" );
         ret = 0;
         goto reset;
     }
     else if( ret != 0 )
     {
         printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
         goto reset;
     }

     printf( " ok\n" );

     /*
      * 6. Read the echo Request
      */
     printf( "  < Read from client:" );
     fflush( stdout );

     len = sizeof( buf ) - 1;
     memset( buf, 0, sizeof( buf ) );

     do ret = mbedtls_ssl_read( &ssl, buf, len );
     while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
            ret == MBEDTLS_ERR_SSL_WANT_WRITE );

     if( ret <= 0 )
     {
         switch( ret )
         {
             case MBEDTLS_ERR_SSL_TIMEOUT:
                 printf( " timeout\n\n" );
                 goto reset;

             case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
                 printf( " connection was closed gracefully\n" );
                 ret = 0;
                 goto close_notify;

             default:
                 printf( " mbedtls_ssl_read returned -0x%x\n\n", (unsigned int) -ret );
                 goto reset;
         }
     }

     len = ret;
     printf( " %d bytes read\n\n%s\n\n", len, buf );

     /*
      * 7. Write the 200 Response
      */
     printf( "  > Write to client:" );
     fflush( stdout );

     do ret = mbedtls_ssl_write( &ssl, buf, len );
     while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
            ret == MBEDTLS_ERR_SSL_WANT_WRITE );

     if( ret < 0 )
     {
         printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n", ret );
         goto exit;
     }

     len = ret;
     printf( " %d bytes written\n\n%s\n\n", len, buf );

     /*
      * 8. Done, cleanly close the connection
      */
 close_notify:
     printf( "  . Closing the connection..." );

     /* No error checking, the connection might be closed already */
     do ret = mbedtls_ssl_close_notify( &ssl );
     while( ret == MBEDTLS_ERR_SSL_WANT_WRITE );
     ret = 0;

     printf( " done\n" );

     goto reset;

     /*
      * Final clean-ups and exit
      */
 exit:

 #ifdef MBEDTLS_ERROR_C
     if( ret != 0 )
     {
         char error_buf[100];
         mbedtls_strerror( ret, error_buf, 100 );
         printf( "Last error was: %d - %s\n\n", ret, error_buf );
     }
 #endif

     mbedtls_net_free( &client_fd );
     mbedtls_net_free( &listen_fd );

     mbedtls_x509_crt_free( &srvcert );
     mbedtls_pk_free( &pkey );
     mbedtls_ssl_free( &ssl );
     mbedtls_ssl_config_free( &conf );
     mbedtls_ssl_cookie_free( &cookie_ctx );
 #if defined(MBEDTLS_SSL_CACHE_C)
     mbedtls_ssl_cache_free( &cache );
 #endif
     mbedtls_ctr_drbg_free( &ctr_drbg );
     mbedtls_entropy_free( &entropy );

     /* Shell can not handle large exit numbers -> 1 for errors */
     if( ret < 0 )
         ret = 1;

     mbedtls_exit( ret );
 }
 #endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_PROTO_DTLS &&
           MBEDTLS_SSL_COOKIE_C && MBEDTLS_NET_C && MBEDTLS_ENTROPY_C &&
           MBEDTLS_CTR_DRBG_C && MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_RSA_C
           && MBEDTLS_PEM_PARSE_C && MBEDTLS_TIMING_C */
	/*
	* Simple DTLS server demonstration program
	*
	* Copyright The Mbed TLS Contributors
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "mbedtls/build_info.h"

	#include "mbedtls/platform.h"

	/* Uncomment out the following line to default to IPv4 and disable IPv6 */
	//#define FORCE_IPV4

	#ifdef FORCE_IPV4
	#define BIND_IP "0.0.0.0" /* Forces IPv4 */
	#else
	#define BIND_IP "::"
	#endif

	#if !defined(MBEDTLS_SSL_SRV_C) \|\| !defined(MBEDTLS_SSL_PROTO_DTLS) \|\| \
	!defined(MBEDTLS_SSL_COOKIE_C) \|\| !defined(MBEDTLS_NET_C) \|\| \
	!defined(MBEDTLS_ENTROPY_C) \|\| !defined(MBEDTLS_CTR_DRBG_C) \|\| \
	!defined(MBEDTLS_X509_CRT_PARSE_C) \|\| !defined(MBEDTLS_RSA_C) \|\| \
	!defined(MBEDTLS_PEM_PARSE_C) \|\| !defined(MBEDTLS_TIMING_C)

	int main( void )
	{
	printf( "MBEDTLS_SSL_SRV_C and/or MBEDTLS_SSL_PROTO_DTLS and/or "
	"MBEDTLS_SSL_COOKIE_C and/or MBEDTLS_NET_C and/or "
	"MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C and/or "
	"MBEDTLS_X509_CRT_PARSE_C and/or MBEDTLS_RSA_C and/or "
	"MBEDTLS_PEM_PARSE_C and/or MBEDTLS_TIMING_C not defined.\n" );
	mbedtls_exit( 0 );
	}
	#else

	#if defined(_WIN32)
	#include <windows.h>
	#endif

	#include <string.h>
	#include <stdlib.h>
	#include <stdio.h>

	#include "mbedtls/entropy.h"
	#include "mbedtls/ctr_drbg.h"
	#include "mbedtls/x509.h"
	#include "mbedtls/ssl.h"
	#include "mbedtls/ssl_cookie.h"
	#include "mbedtls/net_sockets.h"
	#include "mbedtls/error.h"
	#include "mbedtls/debug.h"
	#include "mbedtls/timing.h"

	#include "test/certs.h"

	#if defined(MBEDTLS_SSL_CACHE_C)
	#include "mbedtls/ssl_cache.h"
	#endif

	#define READ_TIMEOUT_MS 10000 /* 10 seconds */
	#define DEBUG_LEVEL 0


	static void my_debug( void *ctx, int level,
	const char *file, int line,
	const char *str )
	{
	((void) level);

	mbedtls_fprintf( (FILE *) ctx, "%s:%04d: %s", file, line, str );
	fflush( (FILE *) ctx );
	}

	int main( void )
	{
	int ret, len;
	mbedtls_net_context listen_fd, client_fd;
	unsigned char buf[1024];
	const char *pers = "dtls_server";
	unsigned char client_ip[16] = { 0 };
	size_t cliip_len;
	mbedtls_ssl_cookie_ctx cookie_ctx;

	mbedtls_entropy_context entropy;
	mbedtls_ctr_drbg_context ctr_drbg;
	mbedtls_ssl_context ssl;
	mbedtls_ssl_config conf;
	mbedtls_x509_crt srvcert;
	mbedtls_pk_context pkey;
	mbedtls_timing_delay_context timer;
	#if defined(MBEDTLS_SSL_CACHE_C)
	mbedtls_ssl_cache_context cache;
	#endif

	mbedtls_net_init( &listen_fd );
	mbedtls_net_init( &client_fd );
	mbedtls_ssl_init( &ssl );
	mbedtls_ssl_config_init( &conf );
	mbedtls_ssl_cookie_init( &cookie_ctx );
	#if defined(MBEDTLS_SSL_CACHE_C)
	mbedtls_ssl_cache_init( &cache );
	#endif
	mbedtls_x509_crt_init( &srvcert );
	mbedtls_pk_init( &pkey );
	mbedtls_entropy_init( &entropy );
	mbedtls_ctr_drbg_init( &ctr_drbg );

	#if defined(MBEDTLS_DEBUG_C)
	mbedtls_debug_set_threshold( DEBUG_LEVEL );
	#endif

	/*
	* 1. Seed the RNG
	*/
	printf( " . Seeding the random number generator..." );
	fflush( stdout );

	if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
	(const unsigned char *) pers,
	strlen( pers ) ) ) != 0 )
	{
	printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
	goto exit;
	}

	printf( " ok\n" );

	/*
	* 2. Load the certificates and private RSA key
	*/
	printf( "\n . Loading the server cert. and key..." );
	fflush( stdout );

	/*
	* This demonstration program uses embedded test certificates.
	* Instead, you may want to use mbedtls_x509_crt_parse_file() to read the
	* server and CA certificates, as well as mbedtls_pk_parse_keyfile().
	*/
	ret = mbedtls_x509_crt_parse( &srvcert, (const unsigned char *) mbedtls_test_srv_crt,
	mbedtls_test_srv_crt_len );
	if( ret != 0 )
	{
	printf( " failed\n ! mbedtls_x509_crt_parse returned %d\n\n", ret );
	goto exit;
	}

	ret = mbedtls_x509_crt_parse( &srvcert, (const unsigned char *) mbedtls_test_cas_pem,
	mbedtls_test_cas_pem_len );
	if( ret != 0 )
	{
	printf( " failed\n ! mbedtls_x509_crt_parse returned %d\n\n", ret );
	goto exit;
	}

	ret = mbedtls_pk_parse_key( &pkey, (const unsigned char *) mbedtls_test_srv_key,
	mbedtls_test_srv_key_len, NULL, 0, mbedtls_ctr_drbg_random, &ctr_drbg );
	if( ret != 0 )
	{
	printf( " failed\n ! mbedtls_pk_parse_key returned %d\n\n", ret );
	goto exit;
	}

	printf( " ok\n" );

	/*
	* 3. Setup the "listening" UDP socket
	*/
	printf( " . Bind on udp/*/4433 ..." );
	fflush( stdout );

	if( ( ret = mbedtls_net_bind( &listen_fd, BIND_IP, "4433", MBEDTLS_NET_PROTO_UDP ) ) != 0 )
	{
	printf( " failed\n ! mbedtls_net_bind returned %d\n\n", ret );
	goto exit;
	}

	printf( " ok\n" );

	/*
	* 4. Setup stuff
	*/
	printf( " . Setting up the DTLS data..." );
	fflush( stdout );

	if( ( ret = mbedtls_ssl_config_defaults( &conf,
	MBEDTLS_SSL_IS_SERVER,
	MBEDTLS_SSL_TRANSPORT_DATAGRAM,
	MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
	goto exit;
	}

	mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
	mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
	mbedtls_ssl_conf_read_timeout( &conf, READ_TIMEOUT_MS );

	#if defined(MBEDTLS_SSL_CACHE_C)
	mbedtls_ssl_conf_session_cache( &conf, &cache,
	mbedtls_ssl_cache_get,
	mbedtls_ssl_cache_set );
	#endif

	mbedtls_ssl_conf_ca_chain( &conf, srvcert.next, NULL );
	if( ( ret = mbedtls_ssl_conf_own_cert( &conf, &srvcert, &pkey ) ) != 0 )
	{
	printf( " failed\n ! mbedtls_ssl_conf_own_cert returned %d\n\n", ret );
	goto exit;
	}

	if( ( ret = mbedtls_ssl_cookie_setup( &cookie_ctx,
	mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
	{
	printf( " failed\n ! mbedtls_ssl_cookie_setup returned %d\n\n", ret );
	goto exit;
	}

	mbedtls_ssl_conf_dtls_cookies( &conf, mbedtls_ssl_cookie_write, mbedtls_ssl_cookie_check,
	&cookie_ctx );

	if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
	{
	printf( " failed\n ! mbedtls_ssl_setup returned %d\n\n", ret );
	goto exit;
	}

	mbedtls_ssl_set_timer_cb( &ssl, &timer, mbedtls_timing_set_delay,
	mbedtls_timing_get_delay );

	printf( " ok\n" );

	reset:
	#ifdef MBEDTLS_ERROR_C
	if( ret != 0 )
	{
	char error_buf[100];
	mbedtls_strerror( ret, error_buf, 100 );
	printf("Last error was: %d - %s\n\n", ret, error_buf );
	}
	#endif

	mbedtls_net_free( &client_fd );

	mbedtls_ssl_session_reset( &ssl );

	/*
	* 3. Wait until a client connects
	*/
	printf( " . Waiting for a remote connection ..." );
	fflush( stdout );

	if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
	client_ip, sizeof( client_ip ), &cliip_len ) ) != 0 )
	{
	printf( " failed\n ! mbedtls_net_accept returned %d\n\n", ret );
	goto exit;
	}

	/* For HelloVerifyRequest cookies */
	if( ( ret = mbedtls_ssl_set_client_transport_id( &ssl,
	client_ip, cliip_len ) ) != 0 )
	{
	printf( " failed\n ! "
	"mbedtls_ssl_set_client_transport_id() returned -0x%x\n\n", (unsigned int) -ret );
	goto exit;
	}

	mbedtls_ssl_set_bio( &ssl, &client_fd,
	mbedtls_net_send, mbedtls_net_recv, mbedtls_net_recv_timeout );

	printf( " ok\n" );

	/*
	* 5. Handshake
	*/
	printf( " . Performing the DTLS handshake..." );
	fflush( stdout );

	do ret = mbedtls_ssl_handshake( &ssl );
	while( ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE );

	if( ret == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED )
	{
	printf( " hello verification requested\n" );
	ret = 0;
	goto reset;
	}
	else if( ret != 0 )
	{
	printf( " failed\n ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
	goto reset;
	}

	printf( " ok\n" );

	/*
	* 6. Read the echo Request
	*/
	printf( " < Read from client:" );
	fflush( stdout );

	len = sizeof( buf ) - 1;
	memset( buf, 0, sizeof( buf ) );

	do ret = mbedtls_ssl_read( &ssl, buf, len );
	while( ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE );

	if( ret <= 0 )
	{
	switch( ret )
	{
	case MBEDTLS_ERR_SSL_TIMEOUT:
	printf( " timeout\n\n" );
	goto reset;

	case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
	printf( " connection was closed gracefully\n" );
	ret = 0;
	goto close_notify;

	default:
	printf( " mbedtls_ssl_read returned -0x%x\n\n", (unsigned int) -ret );
	goto reset;
	}
	}

	len = ret;
	printf( " %d bytes read\n\n%s\n\n", len, buf );

	/*
	* 7. Write the 200 Response
	*/
	printf( " > Write to client:" );
	fflush( stdout );

	do ret = mbedtls_ssl_write( &ssl, buf, len );
	while( ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE );

	if( ret < 0 )
	{
	printf( " failed\n ! mbedtls_ssl_write returned %d\n\n", ret );
	goto exit;
	}

	len = ret;
	printf( " %d bytes written\n\n%s\n\n", len, buf );

	/*
	* 8. Done, cleanly close the connection
	*/
	close_notify:
	printf( " . Closing the connection..." );

	/* No error checking, the connection might be closed already */
	do ret = mbedtls_ssl_close_notify( &ssl );
	while( ret == MBEDTLS_ERR_SSL_WANT_WRITE );
	ret = 0;

	printf( " done\n" );

	goto reset;

	/*
	* Final clean-ups and exit
	*/
	exit:

	#ifdef MBEDTLS_ERROR_C
	if( ret != 0 )
	{
	char error_buf[100];
	mbedtls_strerror( ret, error_buf, 100 );
	printf( "Last error was: %d - %s\n\n", ret, error_buf );
	}
	#endif

	mbedtls_net_free( &client_fd );
	mbedtls_net_free( &listen_fd );

	mbedtls_x509_crt_free( &srvcert );
	mbedtls_pk_free( &pkey );
	mbedtls_ssl_free( &ssl );
	mbedtls_ssl_config_free( &conf );
	mbedtls_ssl_cookie_free( &cookie_ctx );
	#if defined(MBEDTLS_SSL_CACHE_C)
	mbedtls_ssl_cache_free( &cache );
	#endif
	mbedtls_ctr_drbg_free( &ctr_drbg );
	mbedtls_entropy_free( &entropy );

	/* Shell can not handle large exit numbers -> 1 for errors */
	if( ret < 0 )
	ret = 1;

	mbedtls_exit( ret );
	}
	#endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_PROTO_DTLS &&
	MBEDTLS_SSL_COOKIE_C && MBEDTLS_NET_C && MBEDTLS_ENTROPY_C &&
	MBEDTLS_CTR_DRBG_C && MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_RSA_C
	&& MBEDTLS_PEM_PARSE_C && MBEDTLS_TIMING_C */