diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 8e2feb1..5d8969d 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -73,6 +73,7 @@
 #define DFL_REQUEST_SIZE        -1
 #define DFL_DEBUG_LEVEL         0
 #define DFL_NBIO                0
+#define DFL_EVENT               0
 #define DFL_READ_TIMEOUT        0
 #define DFL_MAX_RESEND          0
 #define DFL_CA_FILE             ""
@@ -245,24 +246,26 @@
     "    server_addr=%%s      default: given by name\n"     \
     "    server_port=%%d      default: 4433\n"              \
     "    request_page=%%s     default: \".\"\n"             \
-    "    request_size=%%d     default: about 34 (basic request)\n"           \
+    "    request_size=%%d     default: about 34 (basic request)\n" \
     "                        (minimum: 0, max: " MAX_REQUEST_SIZE_STR " )\n" \
-    "    debug_level=%%d      default: 0 (disabled)\n"      \
-    "    nbio=%%d             default: 0 (blocking I/O)\n"  \
-    "                        options: 1 (non-blocking), 2 (added delays)\n" \
-    "    read_timeout=%%d     default: 0 ms (no timeout)\n"    \
+    "    debug_level=%%d      default: 0 (disabled)\n"             \
+    "    nbio=%%d             default: 0 (blocking I/O)\n"         \
+    "                        options: 1 (non-blocking), 2 (added delays)\n"   \
+    "    event=%%d            default: 0 (loop)\n"                            \
+    "                        options: 1 (level-triggered, implies nbio=1),\n" \
+    "    read_timeout=%%d     default: 0 ms (no timeout)\n"        \
     "    max_resend=%%d       default: 0 (no resend on timeout)\n" \
     "\n"                                                    \
     USAGE_DTLS                                              \
     "\n"                                                    \
-    "    auth_mode=%%s        default: (library default: none)\n"      \
+    "    auth_mode=%%s        default: (library default: none)\n" \
     "                        options: none, optional, required\n" \
     USAGE_IO                                                \
     "\n"                                                    \
     USAGE_PSK                                               \
     USAGE_ECJPAKE                                           \
     "\n"                                                    \
-    "    allow_legacy=%%d     default: (library default: no)\n"      \
+    "    allow_legacy=%%d     default: (library default: no)\n"   \
     USAGE_RENEGO                                            \
     "    exchanges=%%d        default: 1\n"                 \
     "    reconnect=%%d        default: 0 (disabled)\n"      \
@@ -302,7 +305,8 @@
     const char *server_port;    /* port on which the ssl service runs       */
     int debug_level;            /* level of debugging                       */
     int nbio;                   /* should I/O be blocking?                  */
-    uint32_t read_timeout;      /* timeout on mbedtls_ssl_read() in milliseconds    */
+    int event;                  /* loop or event-driven IO? level or edge triggered? */
+    uint32_t read_timeout;      /* timeout on mbedtls_ssl_read() in milliseconds     */
     int max_resend;             /* DTLS times to resend on read timeout     */
     const char *request_page;   /* page on server to request                */
     int request_size;           /* pad request with header to requested size */
@@ -353,7 +357,8 @@
         if( *p == '/' || *p == '\\' )
             basename = p + 1;
 
-    mbedtls_fprintf( (FILE *) ctx, "%s:%04d: |%d| %s", basename, line, level, str );
+    mbedtls_fprintf( (FILE *) ctx, "%s:%04d: |%d| %s",
+                     basename, line, level, str );
     fflush(  (FILE *) ctx  );
 }
 
@@ -399,7 +404,8 @@
 /*
  * Enabled if debug_level > 1 in code below
  */
-static int my_verify( void *data, mbedtls_x509_crt *crt, int depth, uint32_t *flags )
+static int my_verify( void *data, mbedtls_x509_crt *crt,
+                      int depth, uint32_t *flags )
 {
     char buf[1024];
     ((void) data);
@@ -436,6 +442,57 @@
 };
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
+/*
+ * Wait for an event from the underlying transport or the timer
+ * (Used in event-driven IO mode).
+ */
+#if !defined(MBEDTLS_TIMING_C)
+int idle( mbedtls_net_context *fd,
+          int idle_reason )
+#else
+int idle( mbedtls_net_context *fd,
+          mbedtls_timing_delay_context *timer,
+          int idle_reason )
+#endif
+{
+
+    int ret;
+    int poll_type = 0;
+
+    if( idle_reason == MBEDTLS_ERR_SSL_WANT_WRITE )
+        poll_type = MBEDTLS_NET_POLL_WRITE;
+    else if( idle_reason == MBEDTLS_ERR_SSL_WANT_READ )
+        poll_type = MBEDTLS_NET_POLL_READ;
+#if !defined(MBEDTLS_TIMING_C)
+    else
+        return( 0 );
+#endif
+
+    while( 1 )
+    {
+        /* Check if timer has expired */
+#if defined(MBEDTLS_TIMING_C)
+        if( timer != NULL &&
+            mbedtls_timing_get_delay( timer ) == 2 )
+        {
+            break;
+        }
+#endif /* MBEDTLS_TIMING_C */
+
+        /* Check if underlying transport became available */
+        if( poll_type != 0 )
+        {
+            ret = mbedtls_net_poll( fd, poll_type, 0 );
+            if( ret < 0 )
+                return( ret );
+            if( ret == poll_type )
+                break;
+        }
+    }
+
+    return( 0 );
+}
+
 int main( int argc, char *argv[] )
 {
     int ret = 0, len, tail_len, i, written, frags, retry_left;
@@ -521,6 +578,7 @@
     opt.server_port         = DFL_SERVER_PORT;
     opt.debug_level         = DFL_DEBUG_LEVEL;
     opt.nbio                = DFL_NBIO;
+    opt.event               = DFL_EVENT;
     opt.read_timeout        = DFL_READ_TIMEOUT;
     opt.max_resend          = DFL_MAX_RESEND;
     opt.request_page        = DFL_REQUEST_PAGE;
@@ -594,6 +652,12 @@
             if( opt.nbio < 0 || opt.nbio > 2 )
                 goto usage;
         }
+        else if( strcmp( p, "event" ) == 0 )
+        {
+            opt.event = atoi( q );
+            if( opt.event < 0 || opt.event > 2 )
+                goto usage;
+        }
         else if( strcmp( p, "read_timeout" ) == 0 )
             opt.read_timeout = atoi( q );
         else if( strcmp( p, "max_resend" ) == 0 )
@@ -638,16 +702,23 @@
         }
         else if( strcmp( p, "renegotiation" ) == 0 )
         {
-            opt.renegotiation = (atoi( q )) ? MBEDTLS_SSL_RENEGOTIATION_ENABLED :
-                                              MBEDTLS_SSL_RENEGOTIATION_DISABLED;
+            opt.renegotiation = (atoi( q )) ?
+                MBEDTLS_SSL_RENEGOTIATION_ENABLED :
+                MBEDTLS_SSL_RENEGOTIATION_DISABLED;
         }
         else if( strcmp( p, "allow_legacy" ) == 0 )
         {
             switch( atoi( q ) )
             {
-                case -1: opt.allow_legacy = MBEDTLS_SSL_LEGACY_BREAK_HANDSHAKE; break;
-                case 0:  opt.allow_legacy = MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION; break;
-                case 1:  opt.allow_legacy = MBEDTLS_SSL_LEGACY_ALLOW_RENEGOTIATION; break;
+                case -1:
+                    opt.allow_legacy = MBEDTLS_SSL_LEGACY_BREAK_HANDSHAKE;
+                    break;
+                case 0:
+                    opt.allow_legacy = MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION;
+                    break;
+                case 1:
+                    opt.allow_legacy = MBEDTLS_SSL_LEGACY_ALLOW_RENEGOTIATION;
+                    break;
                 default: goto usage;
             }
         }
@@ -704,8 +775,12 @@
         {
             switch( atoi( q ) )
             {
-                case 0: opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_DISABLED; break;
-                case 1: opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_ENABLED; break;
+                case 0:
+                    opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_DISABLED;
+                    break;
+                case 1:
+                    opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_ENABLED;
+                    break;
                 default: goto usage;
             }
         }
@@ -864,6 +939,15 @@
             goto usage;
     }
 
+    /* Event-driven IO is incompatible with the above custom
+     * receive and send functions, as the polling builds on
+     * refers to the underlying net_context. */
+    if( opt.event == 1 && opt.nbio != 1 )
+    {
+        mbedtls_printf( "Warning: event-driven IO mandates nbio=1 - overwrite\n" );
+        opt.nbio = 1;
+    }
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_debug_set_threshold( opt.debug_level );
 #endif
@@ -871,19 +955,20 @@
     if( opt.force_ciphersuite[0] > 0 )
     {
         const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
-        ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( opt.force_ciphersuite[0] );
+        ciphersuite_info =
+            mbedtls_ssl_ciphersuite_from_id( opt.force_ciphersuite[0] );
 
         if( opt.max_version != -1 &&
             ciphersuite_info->min_minor_ver > opt.max_version )
         {
-            mbedtls_printf("forced ciphersuite not allowed with this protocol version\n");
+            mbedtls_printf( "forced ciphersuite not allowed with this protocol version\n" );
             ret = 2;
             goto usage;
         }
         if( opt.min_version != -1 &&
             ciphersuite_info->max_minor_ver < opt.min_version )
         {
-            mbedtls_printf("forced ciphersuite not allowed with this protocol version\n");
+            mbedtls_printf( "forced ciphersuite not allowed with this protocol version\n" );
             ret = 2;
             goto usage;
         }
@@ -909,7 +994,7 @@
         {
             if( opt.arc4 == MBEDTLS_SSL_ARC4_DISABLED )
             {
-                mbedtls_printf("forced RC4 ciphersuite with RC4 disabled\n");
+                mbedtls_printf( "forced RC4 ciphersuite with RC4 disabled\n" );
                 ret = 2;
                 goto usage;
             }
@@ -929,7 +1014,7 @@
 
         if( strlen( opt.psk ) % 2 != 0 )
         {
-            mbedtls_printf("pre-shared key not valid hex\n");
+            mbedtls_printf( "pre-shared key not valid hex\n" );
             goto exit;
         }
 
@@ -946,7 +1031,7 @@
                 c -= 'A' - 10;
             else
             {
-                mbedtls_printf("pre-shared key not valid hex\n");
+                mbedtls_printf( "pre-shared key not valid hex\n" );
                 goto exit;
             }
             psk[ j / 2 ] = c << 4;
@@ -960,7 +1045,7 @@
                 c -= 'A' - 10;
             else
             {
-                mbedtls_printf("pre-shared key not valid hex\n");
+                mbedtls_printf( "pre-shared key not valid hex\n" );
                 goto exit;
             }
             psk[ j / 2 ] |= c;
@@ -1051,11 +1136,12 @@
     fflush( stdout );
 
     mbedtls_entropy_init( &entropy );
-    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
-                               (const unsigned char *) pers,
-                               strlen( pers ) ) ) != 0 )
+    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 -0x%x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
+                        -ret );
         goto exit;
     }
 
@@ -1093,12 +1179,13 @@
 #else
     {
         ret = 1;
-        mbedtls_printf("MBEDTLS_CERTS_C not defined.");
+        mbedtls_printf( "MBEDTLS_CERTS_C not defined." );
     }
 #endif
     if( ret < 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n",
+                        -ret );
         goto exit;
     }
 
@@ -1121,7 +1208,8 @@
     else
 #endif
 #if defined(MBEDTLS_CERTS_C)
-        ret = mbedtls_x509_crt_parse( &clicert, (const unsigned char *) mbedtls_test_cli_crt,
+        ret = mbedtls_x509_crt_parse( &clicert,
+                (const unsigned char *) mbedtls_test_cli_crt,
                 mbedtls_test_cli_crt_len );
 #else
     {
@@ -1131,7 +1219,8 @@
 #endif
     if( ret != 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n",
+                        -ret );
         goto exit;
     }
 
@@ -1144,7 +1233,8 @@
     else
 #endif
 #if defined(MBEDTLS_CERTS_C)
-        ret = mbedtls_pk_parse_key( &pkey, (const unsigned char *) mbedtls_test_cli_key,
+        ret = mbedtls_pk_parse_key( &pkey,
+                (const unsigned char *) mbedtls_test_cli_key,
                 mbedtls_test_cli_key_len, NULL, 0 );
 #else
     {
@@ -1154,7 +1244,8 @@
 #endif
     if( ret != 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_pk_parse_key returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_pk_parse_key returned -0x%x\n\n",
+                        -ret );
         goto exit;
     }
 
@@ -1172,11 +1263,13 @@
             opt.server_addr, opt.server_port );
     fflush( stdout );
 
-    if( ( ret = mbedtls_net_connect( &server_fd, opt.server_addr, opt.server_port,
-                             opt.transport == MBEDTLS_SSL_TRANSPORT_STREAM ?
-                             MBEDTLS_NET_PROTO_TCP : MBEDTLS_NET_PROTO_UDP ) ) != 0 )
+    if( ( ret = mbedtls_net_connect( &server_fd,
+                       opt.server_addr, opt.server_port,
+                       opt.transport == MBEDTLS_SSL_TRANSPORT_STREAM ?
+                       MBEDTLS_NET_PROTO_TCP : MBEDTLS_NET_PROTO_UDP ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_net_connect returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_net_connect returned -0x%x\n\n",
+                        -ret );
         goto exit;
     }
 
@@ -1186,7 +1279,8 @@
         ret = mbedtls_net_set_block( &server_fd );
     if( ret != 0 )
     {
-        mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n",
+                        -ret );
         goto exit;
     }
 
@@ -1203,7 +1297,8 @@
                     opt.transport,
                     MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned -0x%x\n\n",
+                        -ret );
         goto exit;
     }
 
@@ -1226,13 +1321,15 @@
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( opt.hs_to_min != DFL_HS_TO_MIN || opt.hs_to_max != DFL_HS_TO_MAX )
-        mbedtls_ssl_conf_handshake_timeout( &conf, opt.hs_to_min, opt.hs_to_max );
+        mbedtls_ssl_conf_handshake_timeout( &conf, opt.hs_to_min,
+                                            opt.hs_to_max );
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
     if( ( ret = mbedtls_ssl_conf_max_frag_len( &conf, opt.mfl_code ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_max_frag_len returned %d\n\n", ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_max_frag_len returned %d\n\n",
+                        ret );
         goto exit;
     }
 #endif
@@ -1255,8 +1352,8 @@
 #if defined(MBEDTLS_SSL_CBC_RECORD_SPLITTING)
     if( opt.recsplit != DFL_RECSPLIT )
         mbedtls_ssl_conf_cbc_record_splitting( &conf, opt.recsplit
-                                    ? MBEDTLS_SSL_CBC_RECORD_SPLITTING_ENABLED
-                                    : MBEDTLS_SSL_CBC_RECORD_SPLITTING_DISABLED );
+                                  ? MBEDTLS_SSL_CBC_RECORD_SPLITTING_ENABLED
+                                  : MBEDTLS_SSL_CBC_RECORD_SPLITTING_DISABLED );
 #endif
 
 #if defined(MBEDTLS_DHM_C)
@@ -1268,7 +1365,8 @@
     if( opt.alpn_string != NULL )
         if( ( ret = mbedtls_ssl_conf_alpn_protocols( &conf, alpn_list ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_alpn_protocols returned %d\n\n", ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_alpn_protocols returned %d\n\n",
+                            ret );
             goto exit;
         }
 #endif
@@ -1307,7 +1405,8 @@
     {
         if( ( ret = mbedtls_ssl_conf_own_cert( &conf, &clicert, &pkey ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_own_cert returned %d\n\n", ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_own_cert returned %d\n\n",
+                            ret );
             goto exit;
         }
     }
@@ -1326,16 +1425,19 @@
                              (const unsigned char *) opt.psk_identity,
                              strlen( opt.psk_identity ) ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_psk returned %d\n\n", ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_psk returned %d\n\n",
+                        ret );
         goto exit;
     }
 #endif
 
     if( opt.min_version != DFL_MIN_VERSION )
-        mbedtls_ssl_conf_min_version( &conf, MBEDTLS_SSL_MAJOR_VERSION_3, opt.min_version );
+        mbedtls_ssl_conf_min_version( &conf, MBEDTLS_SSL_MAJOR_VERSION_3,
+                                      opt.min_version );
 
     if( opt.max_version != DFL_MAX_VERSION )
-        mbedtls_ssl_conf_max_version( &conf, MBEDTLS_SSL_MAJOR_VERSION_3, opt.max_version );
+        mbedtls_ssl_conf_max_version( &conf, MBEDTLS_SSL_MAJOR_VERSION_3,
+                                      opt.max_version );
 
 #if defined(MBEDTLS_SSL_FALLBACK_SCSV)
     if( opt.fallback != DFL_FALLBACK )
@@ -1344,14 +1446,16 @@
 
     if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned -0x%x\n\n",
+                        -ret );
         goto exit;
     }
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
     if( ( ret = mbedtls_ssl_set_hostname( &ssl, opt.server_name ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n", ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n",
+                        ret );
         goto exit;
     }
 #endif
@@ -1363,7 +1467,8 @@
                         (const unsigned char *) opt.ecjpake_pw,
                                         strlen( opt.ecjpake_pw ) ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_set_hs_ecjpake_password returned %d\n\n", ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_set_hs_ecjpake_password returned %d\n\n",
+                            ret );
             goto exit;
         }
     }
@@ -1372,7 +1477,8 @@
     if( opt.nbio == 2 )
         mbedtls_ssl_set_bio( &ssl, &server_fd, my_send, my_recv, NULL );
     else
-        mbedtls_ssl_set_bio( &ssl, &server_fd, mbedtls_net_send, mbedtls_net_recv,
+        mbedtls_ssl_set_bio( &ssl, &server_fd,
+                             mbedtls_net_send, mbedtls_net_recv,
                              opt.nbio == 0 ? mbedtls_net_recv_timeout : NULL );
 
 #if defined(MBEDTLS_TIMING_C)
@@ -1390,9 +1496,11 @@
 
     while( ( ret = mbedtls_ssl_handshake( &ssl ) ) != 0 )
     {
-        if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
+        if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
+            ret != MBEDTLS_ERR_SSL_WANT_WRITE )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n",
+                            -ret );
             if( ret == MBEDTLS_ERR_X509_CERT_VERIFY_FAILED )
                 mbedtls_printf(
                     "    Unable to verify the server's certificate. "
@@ -1404,10 +1512,23 @@
             mbedtls_printf( "\n" );
             goto exit;
         }
+
+        /* For event-driven IO, wait for socket to become available */
+        if( opt.event == 1 /* level triggered IO */ )
+        {
+#if defined(MBEDTLS_TIMING_C)
+            ret = idle( &server_fd, &timer, ret );
+#else
+            ret = idle( &server_fd, ret );
+#endif
+            if( ret != 0 )
+                goto exit;
+        }
     }
 
     mbedtls_printf( " ok\n    [ Protocol is %s ]\n    [ Ciphersuite is %s ]\n",
-            mbedtls_ssl_get_version( &ssl ), mbedtls_ssl_get_ciphersuite( &ssl ) );
+                    mbedtls_ssl_get_version( &ssl ),
+                    mbedtls_ssl_get_ciphersuite( &ssl ) );
 
     if( ( ret = mbedtls_ssl_get_record_expansion( &ssl ) ) >= 0 )
         mbedtls_printf( "    [ Record expansion is %d ]\n", ret );
@@ -1435,7 +1556,8 @@
 
         if( ( ret = mbedtls_ssl_get_session( &ssl, &saved_session ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_get_session returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_get_session returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
 
@@ -1454,7 +1576,8 @@
 
         mbedtls_printf( " failed\n" );
 
-        mbedtls_x509_crt_verify_info( vrfy_buf, sizeof( vrfy_buf ), "  ! ", flags );
+        mbedtls_x509_crt_verify_info( vrfy_buf, sizeof( vrfy_buf ),
+                                      "  ! ", flags );
 
         mbedtls_printf( "%s\n", vrfy_buf );
     }
@@ -1484,9 +1607,21 @@
             if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
                 ret != MBEDTLS_ERR_SSL_WANT_WRITE )
             {
-                mbedtls_printf( " failed\n  ! mbedtls_ssl_renegotiate returned %d\n\n", ret );
+                mbedtls_printf( " failed\n  ! mbedtls_ssl_renegotiate returned %d\n\n",
+                                ret );
                 goto exit;
             }
+
+            /* For event-driven IO, wait for socket to become available */
+            if( opt.event == 1 /* level triggered IO */ )
+            {
+#if defined(MBEDTLS_TIMING_C)
+                idle( &server_fd, &timer, ret );
+#else
+                idle( &server_fd, ret );
+#endif
+            }
+
         }
         mbedtls_printf( " ok\n" );
     }
@@ -1530,27 +1665,54 @@
     {
         for( written = 0, frags = 0; written < len; written += ret, frags++ )
         {
-            while( ( ret = mbedtls_ssl_write( &ssl, buf + written, len - written ) )
-                           <= 0 )
+            while( ( ret = mbedtls_ssl_write( &ssl, buf + written,
+                                              len - written ) ) <= 0 )
             {
                 if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
                     ret != MBEDTLS_ERR_SSL_WANT_WRITE )
                 {
-                    mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned -0x%x\n\n", -ret );
+                    mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned -0x%x\n\n",
+                                    -ret );
                     goto exit;
                 }
+
+                /* For event-driven IO, wait for socket to become available */
+                if( opt.event == 1 /* level triggered IO */ )
+                {
+#if defined(MBEDTLS_TIMING_C)
+                    idle( &server_fd, &timer, ret );
+#else
+                    idle( &server_fd, ret );
+#endif
+                }
             }
         }
     }
     else /* Not stream, so datagram */
     {
-        do ret = mbedtls_ssl_write( &ssl, buf, len );
-        while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
-               ret == MBEDTLS_ERR_SSL_WANT_WRITE );
+        while( 1 )
+        {
+            ret = mbedtls_ssl_write( &ssl, buf, len );
+
+            if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
+                ret != MBEDTLS_ERR_SSL_WANT_WRITE )
+                break;
+
+            /* For event-driven IO, wait for socket to become available */
+            if( opt.event == 1 /* level triggered IO */ )
+            {
+#if defined(MBEDTLS_TIMING_C)
+                idle( &server_fd, &timer, ret );
+#else
+                idle( &server_fd, ret );
+#endif
+            }
+        }
 
         if( ret < 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n", ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n",
+                            ret );
             goto exit;
         }
 
@@ -1565,7 +1727,8 @@
     }
 
     buf[written] = '\0';
-    mbedtls_printf( " %d bytes written in %d fragments\n\n%s\n", written, frags, (char *) buf );
+    mbedtls_printf( " %d bytes written in %d fragments\n\n%s\n",
+                    written, frags, (char *) buf );
 
     /*
      * 7. Read the HTTP response
@@ -1586,7 +1749,18 @@
 
             if( ret == MBEDTLS_ERR_SSL_WANT_READ ||
                 ret == MBEDTLS_ERR_SSL_WANT_WRITE )
+            {
+                /* For event-driven IO, wait for socket to become available */
+                if( opt.event == 1 /* level triggered IO */ )
+                {
+#if defined(MBEDTLS_TIMING_C)
+                    idle( &server_fd, &timer, ret );
+#else
+                    idle( &server_fd, ret );
+#endif
+                }
                 continue;
+            }
 
             if( ret <= 0 )
             {
@@ -1604,7 +1778,8 @@
                         goto reconnect;
 
                     default:
-                        mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", -ret );
+                        mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n",
+                                        -ret );
                         goto exit;
                 }
             }
@@ -1628,9 +1803,24 @@
         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 );
+        while( 1 )
+        {
+            ret = mbedtls_ssl_read( &ssl, buf, len );
+
+            if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
+                ret != MBEDTLS_ERR_SSL_WANT_WRITE )
+                break;
+
+            /* For event-driven IO, wait for socket to become available */
+            if( opt.event == 1 /* level triggered IO */ )
+            {
+#if defined(MBEDTLS_TIMING_C)
+                idle( &server_fd, &timer, ret );
+#else
+                idle( &server_fd, ret );
+#endif
+            }
+        }
 
         if( ret <= 0 )
         {
@@ -1671,7 +1861,8 @@
 
         if( ( ret = mbedtls_ssl_session_reset( &ssl ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_session_reset returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_session_reset returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
 
@@ -1680,9 +1871,20 @@
             if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
                 ret != MBEDTLS_ERR_SSL_WANT_WRITE )
             {
-                mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
+                mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n",
+                                -ret );
                 goto exit;
             }
+
+            /* For event-driven IO, wait for socket to become available */
+            if( opt.event == 1 /* level triggered IO */ )
+            {
+#if defined(MBEDTLS_TIMING_C)
+                idle( &server_fd, &timer, ret );
+#else
+                idle( &server_fd, ret );
+#endif
+            }
         }
 
         mbedtls_printf( " ok\n" );
@@ -1729,21 +1931,25 @@
 
         if( ( ret = mbedtls_ssl_session_reset( &ssl ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_session_reset returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_session_reset returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
 
         if( ( ret = mbedtls_ssl_set_session( &ssl, &saved_session ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_session returned %d\n\n", ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_session returned %d\n\n",
+                            ret );
             goto exit;
         }
 
-        if( ( ret = mbedtls_net_connect( &server_fd, opt.server_addr, opt.server_port,
-                                 opt.transport == MBEDTLS_SSL_TRANSPORT_STREAM ?
-                                 MBEDTLS_NET_PROTO_TCP : MBEDTLS_NET_PROTO_UDP ) ) != 0 )
+        if( ( ret = mbedtls_net_connect( &server_fd,
+                        opt.server_addr, opt.server_port,
+                        opt.transport == MBEDTLS_SSL_TRANSPORT_STREAM ?
+                        MBEDTLS_NET_PROTO_TCP : MBEDTLS_NET_PROTO_UDP ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_net_connect returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_net_connect returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
 
@@ -1754,7 +1960,7 @@
         if( ret != 0 )
         {
             mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n",
-                    -ret );
+                            -ret );
             goto exit;
         }
 
@@ -1763,7 +1969,8 @@
             if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
                 ret != MBEDTLS_ERR_SSL_WANT_WRITE )
             {
-                mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
+                mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n",
+                                -ret );
                 goto exit;
             }
         }
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 2f3908d..02f9633 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -101,6 +101,7 @@
 #define DFL_SERVER_PORT         "4433"
 #define DFL_DEBUG_LEVEL         0
 #define DFL_NBIO                0
+#define DFL_EVENT               0
 #define DFL_READ_TIMEOUT        0
 #define DFL_CA_FILE             ""
 #define DFL_CA_PATH             ""
@@ -347,6 +348,8 @@
     "    debug_level=%%d      default: 0 (disabled)\n"      \
     "    nbio=%%d             default: 0 (blocking I/O)\n"  \
     "                        options: 1 (non-blocking), 2 (added delays)\n" \
+    "    event=%%d            default: 0 (loop)\n"                            \
+    "                        options: 1 (level-triggered, implies nbio=1),\n" \
     "    read_timeout=%%d     default: 0 ms (no timeout)\n"    \
     "\n"                                                    \
     USAGE_DTLS                                              \
@@ -416,6 +419,7 @@
     const char *server_port;    /* port on which the ssl service runs       */
     int debug_level;            /* level of debugging                       */
     int nbio;                   /* should I/O be blocking?                  */
+    int event;                  /* loop or event-driven IO? level or edge triggered? */
     uint32_t read_timeout;      /* timeout on mbedtls_ssl_read() in milliseconds    */
     const char *ca_file;        /* the file with the CA certificate(s)      */
     const char *ca_path;        /* the path with the CA certificate(s) reside */
@@ -1041,6 +1045,56 @@
 }
 #endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
 
+/*
+ * Wait for an event from the underlying transport or the timer
+ * (Used in event-driven IO mode).
+ */
+#if !defined(MBEDTLS_TIMING_C)
+int idle( mbedtls_net_context *fd,
+          int idle_reason )
+#else
+int idle( mbedtls_net_context *fd,
+          mbedtls_timing_delay_context *timer,
+          int idle_reason )
+#endif
+{
+    int ret;
+    int poll_type = 0;
+
+    if( idle_reason == MBEDTLS_ERR_SSL_WANT_WRITE )
+        poll_type = MBEDTLS_NET_POLL_WRITE;
+    else if( idle_reason == MBEDTLS_ERR_SSL_WANT_READ )
+        poll_type = MBEDTLS_NET_POLL_READ;
+#if !defined(MBEDTLS_TIMING_C)
+    else
+        return( 0 );
+#endif
+
+    while( 1 )
+    {
+        /* Check if timer has expired */
+#if defined(MBEDTLS_TIMING_C)
+        if( timer != NULL &&
+            mbedtls_timing_get_delay( timer ) == 2 )
+        {
+            break;
+        }
+#endif /* MBEDTLS_TIMING_C */
+
+        /* Check if underlying transport became available */
+        if( poll_type != 0 )
+        {
+            ret = mbedtls_net_poll( fd, poll_type, 0 );
+            if( ret < 0 )
+                return( ret );
+            if( ret == poll_type )
+                break;
+        }
+    }
+
+    return( 0 );
+}
+
 int main( int argc, char *argv[] )
 {
     int ret = 0, len, written, frags, exchanges_left;
@@ -1176,6 +1230,7 @@
     opt.server_addr         = DFL_SERVER_ADDR;
     opt.server_port         = DFL_SERVER_PORT;
     opt.debug_level         = DFL_DEBUG_LEVEL;
+    opt.event               = DFL_EVENT;
     opt.nbio                = DFL_NBIO;
     opt.read_timeout        = DFL_READ_TIMEOUT;
     opt.ca_file             = DFL_CA_FILE;
@@ -1258,6 +1313,12 @@
             if( opt.nbio < 0 || opt.nbio > 2 )
                 goto usage;
         }
+        else if( strcmp( p, "event" ) == 0 )
+        {
+            opt.event = atoi( q );
+            if( opt.event < 0 || opt.event > 2 )
+                goto usage;
+        }
         else if( strcmp( p, "read_timeout" ) == 0 )
             opt.read_timeout = atoi( q );
         else if( strcmp( p, "ca_file" ) == 0 )
@@ -1318,16 +1379,23 @@
             opt.version_suites = q;
         else if( strcmp( p, "renegotiation" ) == 0 )
         {
-            opt.renegotiation = (atoi( q )) ? MBEDTLS_SSL_RENEGOTIATION_ENABLED :
-                                              MBEDTLS_SSL_RENEGOTIATION_DISABLED;
+            opt.renegotiation = (atoi( q )) ?
+                MBEDTLS_SSL_RENEGOTIATION_ENABLED :
+                MBEDTLS_SSL_RENEGOTIATION_DISABLED;
         }
         else if( strcmp( p, "allow_legacy" ) == 0 )
         {
             switch( atoi( q ) )
             {
-                case -1: opt.allow_legacy = MBEDTLS_SSL_LEGACY_BREAK_HANDSHAKE; break;
-                case 0:  opt.allow_legacy = MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION; break;
-                case 1:  opt.allow_legacy = MBEDTLS_SSL_LEGACY_ALLOW_RENEGOTIATION; break;
+                case -1:
+                    opt.allow_legacy = MBEDTLS_SSL_LEGACY_BREAK_HANDSHAKE;
+                    break;
+                case 0:
+                    opt.allow_legacy = MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION;
+                    break;
+                case 1:
+                    opt.allow_legacy = MBEDTLS_SSL_LEGACY_ALLOW_RENEGOTIATION;
+                    break;
                 default: goto usage;
             }
         }
@@ -1484,8 +1552,12 @@
         {
             switch( atoi( q ) )
             {
-                case 0: opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_DISABLED; break;
-                case 1: opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_ENABLED; break;
+                case 0:
+                    opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_DISABLED;
+                    break;
+                case 1:
+                    opt.extended_ms = MBEDTLS_SSL_EXTENDED_MS_ENABLED;
+                    break;
                 default: goto usage;
             }
         }
@@ -1558,6 +1630,15 @@
             goto usage;
     }
 
+    /* Event-driven IO is incompatible with the above custom
+     * receive and send functions, as the polling builds on
+     * refers to the underlying net_context. */
+    if( opt.event == 1 && opt.nbio != 1 )
+    {
+        mbedtls_printf( "Warning: event-driven IO mandates nbio=1 - overwrite\n" );
+        opt.nbio = 1;
+    }
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_debug_set_threshold( opt.debug_level );
 #endif
@@ -1565,19 +1646,20 @@
     if( opt.force_ciphersuite[0] > 0 )
     {
         const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
-        ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( opt.force_ciphersuite[0] );
+        ciphersuite_info =
+            mbedtls_ssl_ciphersuite_from_id( opt.force_ciphersuite[0] );
 
         if( opt.max_version != -1 &&
             ciphersuite_info->min_minor_ver > opt.max_version )
         {
-            mbedtls_printf("forced ciphersuite not allowed with this protocol version\n");
+            mbedtls_printf( "forced ciphersuite not allowed with this protocol version\n" );
             ret = 2;
             goto usage;
         }
         if( opt.min_version != -1 &&
             ciphersuite_info->max_minor_ver < opt.min_version )
         {
-            mbedtls_printf("forced ciphersuite not allowed with this protocol version\n");
+            mbedtls_printf( "forced ciphersuite not allowed with this protocol version\n" );
             ret = 2;
             goto usage;
         }
@@ -1756,11 +1838,12 @@
     fflush( stdout );
 
     mbedtls_entropy_init( &entropy );
-    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
-                               (const unsigned char *) pers,
-                               strlen( pers ) ) ) != 0 )
+    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 -0x%x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
+                        -ret );
         goto exit;
     }
 
@@ -1857,7 +1940,7 @@
         if( ( ret = mbedtls_pk_parse_keyfile( &pkey2, opt.key_file2, "" ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile(2) returned -0x%x\n\n",
-                    -ret );
+                            -ret );
             goto exit;
         }
     }
@@ -1875,8 +1958,7 @@
         strcmp( opt.key_file2, "none" ) != 0 )
     {
 #if !defined(MBEDTLS_CERTS_C)
-        mbedtls_printf( "Not certificated or key provided, and \n"
-                "MBEDTLS_CERTS_C not defined!\n" );
+        mbedtls_printf( "Not certificated or key provided, and \nMBEDTLS_CERTS_C not defined!\n" );
         goto exit;
 #else
 #if defined(MBEDTLS_RSA_C)
@@ -1884,14 +1966,16 @@
                                     (const unsigned char *) mbedtls_test_srv_crt_rsa,
                                     mbedtls_test_srv_crt_rsa_len ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
         if( ( ret = mbedtls_pk_parse_key( &pkey,
                                   (const unsigned char *) mbedtls_test_srv_key_rsa,
                                   mbedtls_test_srv_key_rsa_len, NULL, 0 ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_key returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_key returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
         key_cert_init = 2;
@@ -1901,14 +1985,16 @@
                                     (const unsigned char *) mbedtls_test_srv_crt_ec,
                                     mbedtls_test_srv_crt_ec_len ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  !  x509_crt_parse2 returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  x509_crt_parse2 returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
         if( ( ret = mbedtls_pk_parse_key( &pkey2,
                                   (const unsigned char *) mbedtls_test_srv_key_ec,
                                   mbedtls_test_srv_key_ec_len, NULL, 0 ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  !  pk_parse_key2 returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  pk_parse_key2 returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
         key_cert_init2 = 2;
@@ -2303,8 +2389,10 @@
 #if !defined(_WIN32)
     if( received_sigterm )
     {
-        mbedtls_printf( " interrupted by SIGTERM\n" );
-        ret = 0;
+        mbedtls_printf( " interrupted by SIGTERM (not in net_accept())\n" );
+        if( ret == MBEDTLS_ERR_NET_INVALID_CONTEXT )
+            ret = 0;
+
         goto exit;
     }
 #endif
@@ -2340,8 +2428,10 @@
 #if !defined(_WIN32)
         if( received_sigterm )
         {
-            mbedtls_printf( " interrupted by signal\n" );
-            ret = 0;
+            mbedtls_printf( " interrupted by SIGTERM (in net_accept())\n" );
+            if( ret == MBEDTLS_ERR_NET_ACCEPT_FAILED )
+                ret = 0;
+
             goto exit;
         }
 #endif
@@ -2368,8 +2458,8 @@
         if( ( ret = mbedtls_ssl_set_client_transport_id( &ssl,
                         client_ip, cliip_len ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! "
-                    "mbedtls_ssl_set_client_transport_id() returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_set_client_transport_id() returned -0x%x\n\n",
+                            -ret );
             goto exit;
         }
     }
@@ -2397,9 +2487,8 @@
     mbedtls_printf( "  . Performing the SSL/TLS handshake..." );
     fflush( stdout );
 
-    do
+    while( ( ret = mbedtls_ssl_handshake( &ssl ) ) != 0 )
     {
-        ret = mbedtls_ssl_handshake( &ssl );
 #if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
         if( ret == MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS &&
             ssl_async_keys.inject_error == SSL_ASYNC_INJECT_ERROR_CANCEL )
@@ -2408,10 +2497,24 @@
             break;
         }
 #endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
+
+        if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
+            ret != MBEDTLS_ERR_SSL_WANT_WRITE &&
+            ret != MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS )
+            break;
+
+        /* For event-driven IO, wait for socket to become available */
+        if( opt.event == 1 /* level triggered IO */ )
+        {
+#if defined(MBEDTLS_TIMING_C)
+            ret = idle( &client_fd, &timer, ret );
+#else
+            ret = idle( &client_fd, ret );
+#endif
+            if( ret != 0 )
+                goto reset;
+        }
     }
-    while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
-           ret == MBEDTLS_ERR_SSL_WANT_WRITE ||
-           ret == MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS );
 
     if( ret == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED )
     {
@@ -2523,7 +2626,18 @@
             if( ret == MBEDTLS_ERR_SSL_WANT_READ ||
                 ret == MBEDTLS_ERR_SSL_WANT_WRITE ||
                 ret == MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS )
+            {
+                if( opt.event == 1 /* level triggered IO */ )
+                {
+#if defined(MBEDTLS_TIMING_C)
+                    idle( &client_fd, &timer, ret );
+#else
+                    idle( &client_fd, ret );
+#endif
+                }
+
                 continue;
+            }
 
             if( ret <= 0 )
             {
@@ -2611,7 +2725,37 @@
         len = sizeof( buf ) - 1;
         memset( buf, 0, sizeof( buf ) );
 
-        do ret = mbedtls_ssl_read( &ssl, buf, len );
+        do
+        {
+            /* Without the call to `mbedtls_ssl_check_pending`, it might
+             * happen that the client sends application data in the same
+             * datagram as the Finished message concluding the handshake.
+             * In this case, the application data would be ready to be
+             * processed while the underlying transport wouldn't signal
+             * any further incoming data.
+             *
+             * See the test 'Event-driven I/O: session-id resume, UDP packing'
+             * in tests/ssl-opt.sh.
+             */
+
+            /* For event-driven IO, wait for socket to become available */
+            if( mbedtls_ssl_check_pending( &ssl ) == 0 &&
+                opt.event == 1 /* level triggered IO */ )
+            {
+#if defined(MBEDTLS_TIMING_C)
+                idle( &client_fd, &timer, MBEDTLS_ERR_SSL_WANT_READ );
+#else
+                idle( &client_fd, MBEDTLS_ERR_SSL_WANT_READ );
+#endif
+            }
+
+            ret = mbedtls_ssl_read( &ssl, buf, len );
+
+            /* Note that even if `mbedtls_ssl_check_pending` returns true,
+             * it can happen that the subsequent call to `mbedtls_ssl_read`
+             * returns `MBEDTLS_ERR_SSL_WANT_READ`, because the pending messages
+             * might be discarded (e.g. because they are retransmissions). */
+        }
         while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
                ret == MBEDTLS_ERR_SSL_WANT_WRITE ||
                ret == MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS );
@@ -2656,6 +2800,16 @@
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_renegotiate returned %d\n\n", ret );
                 goto reset;
             }
+
+            /* For event-driven IO, wait for socket to become available */
+            if( opt.event == 1 /* level triggered IO */ )
+            {
+#if defined(MBEDTLS_TIMING_C)
+                idle( &client_fd, &timer, ret );
+#else
+                idle( &client_fd, ret );
+#endif
+            }
         }
 
         mbedtls_printf( " ok\n" );
@@ -2691,15 +2845,40 @@
                     mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n", ret );
                     goto reset;
                 }
+
+                /* For event-driven IO, wait for socket to become available */
+                if( opt.event == 1 /* level triggered IO */ )
+                {
+#if defined(MBEDTLS_TIMING_C)
+                    idle( &client_fd, &timer, ret );
+#else
+                    idle( &client_fd, ret );
+#endif
+                }
             }
         }
     }
     else /* Not stream, so datagram */
     {
-        do ret = mbedtls_ssl_write( &ssl, buf, len );
-        while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
-               ret == MBEDTLS_ERR_SSL_WANT_WRITE ||
-               ret == MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS );
+        while( 1 )
+        {
+            ret = mbedtls_ssl_write( &ssl, buf, len );
+
+            if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
+                ret != MBEDTLS_ERR_SSL_WANT_WRITE &&
+                ret != MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS )
+                break;
+
+            /* For event-driven IO, wait for socket to become available */
+            if( opt.event == 1 /* level triggered IO */ )
+            {
+#if defined(MBEDTLS_TIMING_C)
+                idle( &client_fd, &timer, ret );
+#else
+                idle( &client_fd, ret );
+#endif
+            }
+        }
 
         if( ret < 0 )
         {