The SSL server is the one from the examples https://github.com/ARMmbed/mbedtls/blob/development/programs/ssl/ssl_server.c
It is configured on port 8080.
The server runs on the linux operating system

Linux commands give the following:
uname -a
Linux termv7 4.15.0-91-generic #92-Ubuntu SMP Fri Feb 28 11:09:48 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

On the client side, the sim800 module is used.

Log files attached to the email.

File contents TermV-terminals-server.key:

subject=/C=RU/ST=Sample/L=Sample/O=Sample/OU=Sample/CN=localhost
issuer=/C=RU/ST=Sample/L=Sample/O=Sample/OU=Sample/CN=Sample
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

File contents TermV-terminals-server.crt:

Server sources:

#include <stdio.h>

/*
* SSL 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.
*/

#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#include <stdlib.h>
#define mbedtls_time time
#define mbedtls_time_t time_t
#define mbedtls_fprintf fprintf
#define mbedtls_printf printf
#define mbedtls_exit exit
#define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
#define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
#endif

#if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_CERTS_C) || \
!defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_SSL_TLS_C) || \
!defined(MBEDTLS_SSL_SRV_C) || !defined(MBEDTLS_NET_C) || \
!defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_CTR_DRBG_C) || \
!defined(MBEDTLS_X509_CRT_PARSE_C) || !defined(MBEDTLS_FS_IO) || \
!defined(MBEDTLS_PEM_PARSE_C)
int main( void )
{
mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_CERTS_C and/or MBEDTLS_ENTROPY_C "
"and/or MBEDTLS_SSL_TLS_C and/or MBEDTLS_SSL_SRV_C and/or "
"MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
"MBEDTLS_CTR_DRBG_C and/or MBEDTLS_X509_CRT_PARSE_C "
"and/or MBEDTLS_PEM_PARSE_C not defined.\n");
mbedtls_exit( 0 );
}
#else

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

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

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

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

#define HTTP_RESPONSE \
"HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n" \
"<h2>mbed TLS Test Server</h2>\r\n" \
"<p>Successful connection using: %s</p>\r\n"

#define DEBUG_LEVEL 5

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 = "ssl_server";

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;
#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 );
#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. Load the certificates and private RSA key
*/
mbedtls_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_file( &srvcert,"/etc/minpay/cert/TermV-terminals-server.crt");

if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_x509_crt_parse returned %d\n\n", ret );
goto exit;
}

ret = mbedtls_pk_parse_keyfile( &pkey,"/etc/minpay/cert/TermV-terminals-server.key", NULL );

if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_x509_crt_parse returned %d\n\n", ret );
goto exit;
}

mbedtls_printf( " ok\n" );

/*
* 2. Setup the listening TCP socket
*/
mbedtls_printf( " . Bind on https://localhost:8080/ ..." );
fflush( stdout );

if( ( ret = mbedtls_net_bind( &listen_fd, NULL, "8080", MBEDTLS_NET_PROTO_TCP ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_net_bind returned %d\n\n", ret );
goto exit;
}

mbedtls_printf( " ok\n" );

/*
* 3. Seed the RNG
*/
mbedtls_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 )
{
mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
goto exit;
}

mbedtls_printf( " ok\n" );

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

if( ( ret = mbedtls_ssl_config_defaults( &conf,
MBEDTLS_SSL_IS_SERVER,
MBEDTLS_SSL_TRANSPORT_STREAM,
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 );

#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 )
{
mbedtls_printf( " failed\n ! mbedtls_ssl_conf_own_cert returned %d\n\n", ret );
goto exit;
}

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

mbedtls_printf( " ok\n" );

reset:
#ifdef MBEDTLS_ERROR_C
if( ret != 0 )
{
char error_buf[100];
mbedtls_strerror( ret, error_buf, 100 );
mbedtls_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
*/
mbedtls_printf( " . Waiting for a remote connection ..." );
fflush( stdout );

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

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

mbedtls_printf( " ok\n" );

/*
* 5. Handshake
*/
mbedtls_printf( " . Performing the SSL/TLS handshake..." );
fflush( stdout );

while( ( ret = mbedtls_ssl_handshake( &ssl ) ) != 0 )
{
if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
{
mbedtls_printf( " failed\n ! mbedtls_ssl_handshake returned %d\n\n", ret );
goto reset;
}
}

mbedtls_printf( " ok\n" );

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

do
{
len = sizeof( buf ) - 1;
memset( buf, 0, sizeof( buf ) );
ret = mbedtls_ssl_read( &ssl, buf, len );

if( ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE )
continue;

if( ret <= 0 )
{
switch( ret )
{
case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
mbedtls_printf( " connection was closed gracefully\n" );
break;

case MBEDTLS_ERR_NET_CONN_RESET:
mbedtls_printf( " connection was reset by peer\n" );
break;

default:
mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", (unsigned int) -ret );
break;
}

break;
}

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

if( ret > 0 )
break;
}
while( 1 );

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

len = sprintf( (char *) buf, HTTP_RESPONSE,
mbedtls_ssl_get_ciphersuite( &ssl ) );

while( ( ret = mbedtls_ssl_write( &ssl, buf, len ) ) <= 0 )
{
if( ret == MBEDTLS_ERR_NET_CONN_RESET )
{
mbedtls_printf( " failed\n ! peer closed the connection\n\n" );
goto reset;
}

if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
{
mbedtls_printf( " failed\n ! mbedtls_ssl_write returned %d\n\n", ret );
goto exit;
}
}

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

mbedtls_printf( " . Closing the connection..." );

while( ( ret = mbedtls_ssl_close_notify( &ssl ) ) < 0 )
{
if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
ret != MBEDTLS_ERR_SSL_WANT_WRITE )
{
mbedtls_printf( " failed\n ! mbedtls_ssl_close_notify returned %d\n\n", ret );
goto reset;
}
}

mbedtls_printf( " ok\n" );

ret = 0;
goto reset;

exit:

#ifdef MBEDTLS_ERROR_C
if( ret != 0 )
{
char error_buf[100];
mbedtls_strerror( ret, error_buf, 100 );
mbedtls_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 );
#if defined(MBEDTLS_SSL_CACHE_C)
mbedtls_ssl_cache_free( &cache );
#endif
mbedtls_ctr_drbg_free( &ctr_drbg );
mbedtls_entropy_free( &entropy );

#if defined(_WIN32)
mbedtls_printf( " Press Enter to exit this program.\n" );
fflush( stdout ); getchar();
#endif

mbedtls_exit( ret );
}
#endif /* MBEDTLS_BIGNUM_C && MBEDTLS_CERTS_C && MBEDTLS_ENTROPY_C &&
MBEDTLS_SSL_TLS_C && MBEDTLS_SSL_SRV_C && MBEDTLS_NET_C &&
MBEDTLS_RSA_C && MBEDTLS_CTR_DRBG_C && MBEDTLS_X509_CRT_PARSE_C
&& MBEDTLS_FS_IO && MBEDTLS_PEM_PARSE_C */