diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index e9523ce..3ccfa6d 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -71,7 +71,7 @@
 
     int ret;
     size_t n, buflen;
-    int server_fd = -1;
+    mbedtls_net_context server_fd;
 
     unsigned char *p, *end;
     unsigned char buf[2048];
@@ -84,7 +84,8 @@
     mbedtls_dhm_context dhm;
     mbedtls_aes_context aes;
 
-    memset( &rsa, 0, sizeof( rsa ) );
+    mbedtls_net_init( &server_fd );
+    mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
     mbedtls_dhm_init( &dhm );
     mbedtls_aes_init( &aes );
     mbedtls_ctr_drbg_init( &ctr_drbg );
@@ -280,8 +281,7 @@
 
 exit:
 
-    if( server_fd != -1 )
-        mbedtls_net_close( server_fd );
+    mbedtls_net_close( &server_fd );
 
     mbedtls_aes_free( &aes );
     mbedtls_rsa_free( &rsa );
diff --git a/programs/pkey/dh_server.c b/programs/pkey/dh_server.c
index 30abaa8..71fa737 100644
--- a/programs/pkey/dh_server.c
+++ b/programs/pkey/dh_server.c
@@ -71,8 +71,7 @@
 
     int ret;
     size_t n, buflen;
-    int listen_fd = -1;
-    int client_fd = -1;
+    mbedtls_net_context listen_fd, client_fd;
 
     unsigned char buf[2048];
     unsigned char hash[20];
@@ -85,7 +84,9 @@
     mbedtls_dhm_context dhm;
     mbedtls_aes_context aes;
 
-    memset( &rsa, 0, sizeof( rsa ) );
+    mbedtls_net_init( &listen_fd );
+    mbedtls_net_init( &client_fd );
+    mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
     mbedtls_dhm_init( &dhm );
     mbedtls_aes_init( &aes );
     mbedtls_ctr_drbg_init( &ctr_drbg );
@@ -173,7 +174,7 @@
         goto exit;
     }
 
-    if( ( ret = mbedtls_net_accept( listen_fd, &client_fd,
+    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 );
@@ -282,8 +283,8 @@
 
 exit:
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
+    mbedtls_net_close( &listen_fd );
 
     mbedtls_aes_free( &aes );
     mbedtls_rsa_free( &rsa );
diff --git a/programs/ssl/dtls_client.c b/programs/ssl/dtls_client.c
index 0fedbc7..b3cfb31 100644
--- a/programs/ssl/dtls_client.c
+++ b/programs/ssl/dtls_client.c
@@ -83,7 +83,8 @@
 
 int main( int argc, char *argv[] )
 {
-    int ret, len, server_fd = -1;
+    int ret, len;
+    mbedtls_net_context server_fd;
     uint32_t flags;
     unsigned char buf[1024];
     const char *pers = "dtls_client";
@@ -106,6 +107,7 @@
     /*
      * 0. Initialize the RNG and the session data
      */
+    mbedtls_net_init( &server_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     mbedtls_x509_crt_init( &cacert );
@@ -324,8 +326,7 @@
     }
 #endif
 
-    if( server_fd != -1 )
-        mbedtls_net_close( server_fd );
+    mbedtls_net_close( &server_fd );
 
     mbedtls_x509_crt_free( &cacert );
     mbedtls_ssl_free( &ssl );
diff --git a/programs/ssl/dtls_server.c b/programs/ssl/dtls_server.c
index ef7ce94..e1da0f7 100644
--- a/programs/ssl/dtls_server.c
+++ b/programs/ssl/dtls_server.c
@@ -92,8 +92,7 @@
 int main( void )
 {
     int ret, len;
-    int listen_fd;
-    int client_fd = -1;
+    mbedtls_net_context listen_fd, client_fd;
     unsigned char buf[1024];
     const char *pers = "dtls_server";
     unsigned char client_ip[16] = { 0 };
@@ -111,6 +110,8 @@
     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 );
@@ -255,20 +256,17 @@
     }
 #endif
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
 
     mbedtls_ssl_session_reset( &ssl );
 
     /*
      * 3. Wait until a client connects
      */
-    client_fd = -1;
-
     printf( "  . Waiting for a remote connection ..." );
     fflush( stdout );
 
-    if( ( ret = mbedtls_net_accept( listen_fd, &client_fd,
+    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 );
@@ -403,8 +401,8 @@
     }
 #endif
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
+    mbedtls_net_close( &listen_fd );
 
     mbedtls_x509_crt_free( &srvcert );
     mbedtls_pk_free( &pkey );
diff --git a/programs/ssl/mini_client.c b/programs/ssl/mini_client.c
index 2d1dcb9..95b0f92 100644
--- a/programs/ssl/mini_client.c
+++ b/programs/ssl/mini_client.c
@@ -32,6 +32,10 @@
  * NET module, in order to avoid the overhead of getaddrinfo() which tends to
  * dominate memory usage in small configurations. For the sake of simplicity,
  * only a Unix version is implemented.
+ *
+ * Warning: we are breaking some of the abtractions from the NET layer here.
+ * This is not a good example for general use. This programs has the specific
+ * goal of minimizing use of the libc functions on full-blown OSes.
  */
 #if defined(unix) || defined(__unix__) || defined(__unix)
 #define UNIX
@@ -160,7 +164,7 @@
 int main( void )
 {
     int ret = exit_ok;
-    int server_fd = -1;
+    mbedtls_net_context server_fd;
     struct sockaddr_in addr;
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
     mbedtls_x509_crt ca;
@@ -175,6 +179,7 @@
     /*
      * 0. Initialize and setup stuff
      */
+    mbedtls_net_init( &server_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
@@ -241,13 +246,13 @@
     addr.sin_addr.s_addr = *((char *) &ret) == ret ? ADDR_LE : ADDR_BE;
     ret = 0;
 
-    if( ( server_fd = socket( AF_INET, SOCK_STREAM, 0 ) ) < 0 )
+    if( ( server_fd.fd = socket( AF_INET, SOCK_STREAM, 0 ) ) < 0 )
     {
         ret = socket_failed;
         goto exit;
     }
 
-    if( connect( server_fd,
+    if( connect( server_fd.fd,
                 (const struct sockaddr *) &addr, sizeof( addr ) ) < 0 )
     {
         ret = connect_failed;
@@ -275,8 +280,7 @@
     mbedtls_ssl_close_notify( &ssl );
 
 exit:
-    if( server_fd != -1 )
-        mbedtls_net_close( server_fd );
+    mbedtls_net_close( &server_fd );
 
     mbedtls_ssl_free( &ssl );
     mbedtls_ssl_config_free( &conf );
diff --git a/programs/ssl/ssl_client1.c b/programs/ssl/ssl_client1.c
index c23c653..61ead50 100644
--- a/programs/ssl/ssl_client1.c
+++ b/programs/ssl/ssl_client1.c
@@ -78,7 +78,8 @@
 
 int main( void )
 {
-    int ret, len, server_fd = -1;
+    int ret, len;
+    mbedtls_net_context server_fd;
     uint32_t flags;
     unsigned char buf[1024];
     const char *pers = "ssl_client1";
@@ -96,6 +97,7 @@
     /*
      * 0. Initialize the RNG and the session data
      */
+    mbedtls_net_init( &server_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     mbedtls_x509_crt_init( &cacert );
@@ -288,8 +290,7 @@
     }
 #endif
 
-    if( server_fd != -1 )
-        mbedtls_net_close( server_fd );
+    mbedtls_net_close( &server_fd );
 
     mbedtls_x509_crt_free( &cacert );
     mbedtls_ssl_free( &ssl );
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index f8188d6..27bd8bf 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -386,7 +386,8 @@
 
 int main( int argc, char *argv[] )
 {
-    int ret = 0, len, tail_len, server_fd, i, written, frags, retry_left;
+    int ret = 0, len, tail_len, i, written, frags, retry_left;
+    mbedtls_net_context server_fd;
     unsigned char buf[MBEDTLS_SSL_MAX_CONTENT_LEN + 1];
 #if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
     unsigned char psk[MBEDTLS_PSK_MAX_LEN];
@@ -417,7 +418,7 @@
     /*
      * Make sure memory references are valid.
      */
-    server_fd = 0;
+    mbedtls_net_init( &server_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     memset( &saved_session, 0, sizeof( mbedtls_ssl_session ) );
@@ -1038,9 +1039,9 @@
     }
 
     if( opt.nbio > 0 )
-        ret = mbedtls_net_set_nonblock( server_fd );
+        ret = mbedtls_net_set_nonblock( &server_fd );
     else
-        ret = mbedtls_net_set_block( server_fd );
+        ret = mbedtls_net_set_block( &server_fd );
     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n", -ret );
@@ -1502,7 +1503,7 @@
     {
         --opt.reconnect;
 
-        mbedtls_net_close( server_fd );
+        mbedtls_net_close( &server_fd );
 
 #if defined(MBEDTLS_TIMING_C)
         if( opt.reco_delay > 0 )
@@ -1533,9 +1534,9 @@
         }
 
         if( opt.nbio > 0 )
-            ret = mbedtls_net_set_nonblock( server_fd );
+            ret = mbedtls_net_set_nonblock( &server_fd );
         else
-            ret = mbedtls_net_set_block( server_fd );
+            ret = mbedtls_net_set_block( &server_fd );
         if( ret != 0 )
         {
             mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n",
@@ -1571,8 +1572,7 @@
     }
 #endif
 
-    if( server_fd )
-        mbedtls_net_close( server_fd );
+    mbedtls_net_close( &server_fd );
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
     mbedtls_x509_crt_free( &clicert );
diff --git a/programs/ssl/ssl_fork_server.c b/programs/ssl/ssl_fork_server.c
index 0984be1..9aab975 100644
--- a/programs/ssl/ssl_fork_server.c
+++ b/programs/ssl/ssl_fork_server.c
@@ -96,8 +96,7 @@
 int main( void )
 {
     int ret, len, cnt = 0, pid;
-    int listen_fd;
-    int client_fd = -1;
+    mbedtls_net_context listen_fd, client_fd;
     unsigned char buf[1024];
     const char *pers = "ssl_fork_server";
 
@@ -108,6 +107,8 @@
     mbedtls_x509_crt srvcert;
     mbedtls_pk_context pkey;
 
+    mbedtls_net_init( &listen_fd );
+    mbedtls_net_init( &client_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     mbedtls_entropy_init( &entropy );
@@ -216,13 +217,13 @@
         /*
          * 3. Wait until a client connects
          */
-        client_fd = -1;
-        memset( &ssl, 0, sizeof( ssl ) );
+        mbedtls_net_init( &client_fd );
+        mbedtls_ssl_init( &ssl );
 
         mbedtls_printf( "  . Waiting for a remote connection ..." );
         fflush( stdout );
 
-        if( ( ret = mbedtls_net_accept( listen_fd, &client_fd,
+        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 );
@@ -258,11 +259,11 @@
                 goto exit;
             }
 
-            close( client_fd );
+            mbedtls_net_close( &client_fd );
             continue;
         }
 
-        close( listen_fd );
+        mbedtls_net_close( &listen_fd );
 
         /*
          * 4. Setup stuff
@@ -384,9 +385,8 @@
     }
 
 exit:
-
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
+    mbedtls_net_close( &listen_fd );
 
     mbedtls_x509_crt_free( &srvcert );
     mbedtls_pk_free( &pkey );
diff --git a/programs/ssl/ssl_mail_client.c b/programs/ssl/ssl_mail_client.c
index 9932594..4ea5d4c 100644
--- a/programs/ssl/ssl_mail_client.c
+++ b/programs/ssl/ssl_mail_client.c
@@ -66,8 +66,6 @@
 #include <unistd.h>
 #else
 #include <io.h>
-#define read _read
-#define write _write
 #endif
 
 #if defined(_WIN32) || defined(_WIN32_WCE)
@@ -294,7 +292,7 @@
     while( 1 );
 }
 
-static int write_and_get_response( int sock_fd, unsigned char *buf, size_t len )
+static int write_and_get_response( mbedtls_net_context *sock_fd, unsigned char *buf, size_t len )
 {
     int ret;
     unsigned char data[128];
@@ -302,7 +300,7 @@
     size_t i, idx = 0;
 
     mbedtls_printf("\n%s", buf);
-    if( len && ( ret = write( sock_fd, buf, len ) ) <= 0 )
+    if( len && ( ret = mbedtls_net_send( sock_fd, buf, len ) ) <= 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n", ret );
             return -1;
@@ -312,7 +310,7 @@
     {
         len = sizeof( data ) - 1;
         memset( data, 0, sizeof( data ) );
-        ret = read( sock_fd, data, len );
+        ret = mbedtls_net_recv( sock_fd, data, len );
 
         if( ret <= 0 )
         {
@@ -346,7 +344,8 @@
 
 int main( int argc, char *argv[] )
 {
-    int ret = 0, len, server_fd;
+    int ret = 0, len;
+    mbedtls_net_context server_fd;
     unsigned char buf[1024];
 #if defined(MBEDTLS_BASE64_C)
     unsigned char base[1024];
@@ -369,7 +368,7 @@
     /*
      * Make sure memory references are valid in case we exit early.
      */
-    server_fd = 0;
+    mbedtls_net_init( &server_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     memset( &buf, 0, sizeof( buf ) );
@@ -658,7 +657,7 @@
         mbedtls_printf( "  > Get header from server:" );
         fflush( stdout );
 
-        ret = write_and_get_response( server_fd, buf, 0 );
+        ret = write_and_get_response( &server_fd, buf, 0 );
         if( ret < 200 || ret > 299 )
         {
             mbedtls_printf( " failed\n  ! server responded with %d\n\n", ret );
@@ -672,7 +671,7 @@
 
         gethostname( hostname, 32 );
         len = sprintf( (char *) buf, "EHLO %s\r\n", hostname );
-        ret = write_and_get_response( server_fd, buf, len );
+        ret = write_and_get_response( &server_fd, buf, len );
         if( ret < 200 || ret > 299 )
         {
             mbedtls_printf( " failed\n  ! server responded with %d\n\n", ret );
@@ -686,7 +685,7 @@
 
         gethostname( hostname, 32 );
         len = sprintf( (char *) buf, "STARTTLS\r\n" );
-        ret = write_and_get_response( server_fd, buf, len );
+        ret = write_and_get_response( &server_fd, buf, len );
         if( ret < 200 || ret > 299 )
         {
             mbedtls_printf( " failed\n  ! server responded with %d\n\n", ret );
@@ -820,8 +819,7 @@
 
 exit:
 
-    if( server_fd )
-        mbedtls_net_close( server_fd );
+    mbedtls_net_close( &server_fd );
     mbedtls_x509_crt_free( &clicert );
     mbedtls_x509_crt_free( &cacert );
     mbedtls_pk_free( &pkey );
diff --git a/programs/ssl/ssl_pthread_server.c b/programs/ssl/ssl_pthread_server.c
index 7a4c2b2..4bd3671 100644
--- a/programs/ssl/ssl_pthread_server.c
+++ b/programs/ssl/ssl_pthread_server.c
@@ -106,7 +106,7 @@
 }
 
 typedef struct {
-    int client_fd;
+    mbedtls_net_context client_fd;
     int thread_complete;
     const mbedtls_ssl_config *config;
 } thread_info_t;
@@ -124,7 +124,7 @@
 {
     int ret, len;
     thread_info_t *thread_info = (thread_info_t *) data;
-    int client_fd = thread_info->client_fd;
+    mbedtls_net_context *client_fd = &thread_info->client_fd;
     long int thread_id = (long int) pthread_self();
     unsigned char buf[1024];
     mbedtls_ssl_context ssl;
@@ -132,7 +132,7 @@
     /* Make sure memory references are valid */
     mbedtls_ssl_init( &ssl );
 
-    mbedtls_printf( "  [ #%ld ]  Client FD %d\n", thread_id, client_fd );
+    mbedtls_printf( "  [ #%ld ]  Setting up SSL/TLS data\n", thread_id );
 
     /*
      * 4. Get the SSL context ready
@@ -144,7 +144,7 @@
         goto thread_exit;
     }
 
-    mbedtls_ssl_set_bio( &ssl, &client_fd, mbedtls_net_send, mbedtls_net_recv, NULL );
+    mbedtls_ssl_set_bio( &ssl, client_fd, mbedtls_net_send, mbedtls_net_recv, NULL );
 
     /*
      * 5. Handshake
@@ -273,7 +273,7 @@
     return( NULL );
 }
 
-static int thread_create( int client_fd )
+static int thread_create( mbedtls_net_context *client_fd )
 {
     int ret, i;
 
@@ -302,9 +302,10 @@
      */
     memcpy( &threads[i].data, &base_info, sizeof(base_info) );
     threads[i].active = 1;
-    threads[i].data.client_fd = client_fd;
+    memcpy( &threads[i].data.client_fd, client_fd, sizeof( mbedtls_net_context ) );
 
-    if( ( ret = pthread_create( &threads[i].thread, NULL, handle_ssl_connection,                                &threads[i].data ) ) != 0 )
+    if( ( ret = pthread_create( &threads[i].thread, NULL, handle_ssl_connection,
+                                &threads[i].data ) ) != 0 )
     {
         return( ret );
     }
@@ -315,8 +316,7 @@
 int main( void )
 {
     int ret;
-    int listen_fd;
-    int client_fd = -1;
+    mbedtls_net_context listen_fd, client_fd;
     const char pers[] = "ssl_pthread_server";
 
     mbedtls_entropy_context entropy;
@@ -346,6 +346,8 @@
     mbedtls_ssl_config_init( &conf );
     mbedtls_ctr_drbg_init( &ctr_drbg );
     memset( threads, 0, sizeof(threads) );
+    mbedtls_net_init( &listen_fd );
+    mbedtls_net_init( &client_fd );
 
     mbedtls_mutex_init( &debug_mutex );
 
@@ -474,11 +476,9 @@
     /*
      * 3. Wait until a client connects
      */
-    client_fd = -1;
-
     mbedtls_printf( "  [ main ]  Waiting for a remote connection\n" );
 
-    if( ( ret = mbedtls_net_accept( listen_fd, &client_fd,
+    if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
                                     NULL, 0, NULL ) ) != 0 )
     {
         mbedtls_printf( "  [ main ] failed: mbedtls_net_accept returned -0x%04x\n", ret );
@@ -488,10 +488,10 @@
     mbedtls_printf( "  [ main ]  ok\n" );
     mbedtls_printf( "  [ main ]  Creating a new thread\n" );
 
-    if( ( ret = thread_create( client_fd ) ) != 0 )
+    if( ( ret = thread_create( &client_fd ) ) != 0 )
     {
         mbedtls_printf( "  [ main ]  failed: thread_create returned %d\n", ret );
-        mbedtls_net_close( client_fd );
+        mbedtls_net_close( &client_fd );
         goto reset;
     }
 
@@ -508,6 +508,8 @@
     mbedtls_entropy_free( &entropy );
     mbedtls_ssl_config_free( &conf );
 
+    mbedtls_net_free( &listen_fd );
+
     mbedtls_mutex_free( &debug_mutex );
 
 #if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
diff --git a/programs/ssl/ssl_server.c b/programs/ssl/ssl_server.c
index c009733..786ae5c 100644
--- a/programs/ssl/ssl_server.c
+++ b/programs/ssl/ssl_server.c
@@ -91,8 +91,7 @@
 int main( void )
 {
     int ret, len;
-    int listen_fd;
-    int client_fd = -1;
+    mbedtls_net_context listen_fd, client_fd;
     unsigned char buf[1024];
     const char *pers = "ssl_server";
 
@@ -106,6 +105,8 @@
     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)
@@ -236,20 +237,17 @@
     }
 #endif
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
 
     mbedtls_ssl_session_reset( &ssl );
 
     /*
      * 3. Wait until a client connects
      */
-    client_fd = -1;
-
     mbedtls_printf( "  . Waiting for a remote connection ..." );
     fflush( stdout );
 
-    if( ( ret = mbedtls_net_accept( listen_fd, &client_fd,
+    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 );
@@ -375,8 +373,8 @@
     }
 #endif
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
+    mbedtls_net_close( &listen_fd );
 
     mbedtls_x509_crt_free( &srvcert );
     mbedtls_pk_free( &pkey );
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index c66a4e9..3b2c802 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -746,7 +746,7 @@
 }
 #endif /* MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED */
 
-static int listen_fd, client_fd = -1;
+static mbedtls_net_context listen_fd, client_fd;
 
 /* Interruption handler to ensure clean exit (for valgrind testing) */
 #if !defined(_WIN32)
@@ -755,8 +755,8 @@
 {
     ((void) sig);
     received_sigterm = 1;
-    mbedtls_net_close( listen_fd ); /* causes mbedtls_net_accept() to abort */
-    mbedtls_net_close( client_fd ); /* causes net_read() to abort */
+    mbedtls_net_close( &listen_fd ); /* causes mbedtls_net_accept() to abort */
+    mbedtls_net_close( &client_fd ); /* causes net_read() to abort */
 }
 #endif
 
@@ -826,7 +826,8 @@
     /*
      * Make sure memory references are valid in case we exit early.
      */
-    listen_fd = 0;
+    mbedtls_net_init( &client_fd );
+    mbedtls_net_init( &listen_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     mbedtls_ctr_drbg_init( &ctr_drbg );
@@ -1842,20 +1843,17 @@
     }
 #endif
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
 
     mbedtls_ssl_session_reset( &ssl );
 
     /*
      * 3. Wait until a client connects
      */
-    client_fd = -1;
-
     mbedtls_printf( "  . Waiting for a remote connection ..." );
     fflush( stdout );
 
-    if( ( ret = mbedtls_net_accept( listen_fd, &client_fd,
+    if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
                     client_ip, sizeof( client_ip ), &cliip_len ) ) != 0 )
     {
 #if !defined(_WIN32)
@@ -1872,9 +1870,9 @@
     }
 
     if( opt.nbio > 0 )
-        ret = mbedtls_net_set_nonblock( client_fd );
+        ret = mbedtls_net_set_nonblock( &client_fd );
     else
-        ret = mbedtls_net_set_block( client_fd );
+        ret = mbedtls_net_set_block( &client_fd );
     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n", -ret );
@@ -2254,8 +2252,8 @@
     mbedtls_printf( "  . Cleaning up..." );
     fflush( stdout );
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
+    mbedtls_net_close( &client_fd );
+    mbedtls_net_close( &listen_fd );
 
 #if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_FS_IO)
     mbedtls_dhm_free( &dhm );
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index f91d42f..9962445 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -20,6 +20,12 @@
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+/*
+ * Warning: this is an internal utility program we use for tests.
+ * It does break some abstractions from the NET layer, and is thus NOT an
+ * example of good general usage.
+ */
+
 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
@@ -284,7 +290,7 @@
 
 typedef struct
 {
-    int dst;
+    mbedtls_net_context *dst;
     const char *way;
     const char *type;
     unsigned len;
@@ -306,7 +312,7 @@
 int send_packet( const packet *p, const char *why )
 {
     int ret;
-    int dst = p->dst;
+    mbedtls_net_context *dst = p->dst;
 
     /* insert corrupted ApplicationData record? */
     if( opt.bad_ad &&
@@ -317,7 +323,7 @@
         ++buf[p->len - 1];
 
         print_packet( p, "corrupted" );
-        if( ( ret = mbedtls_net_send( &dst, buf, p->len ) ) <= 0 )
+        if( ( ret = mbedtls_net_send( dst, buf, p->len ) ) <= 0 )
         {
             mbedtls_printf( "  ! mbedtls_net_send returned %d\n", ret );
             return( ret );
@@ -325,7 +331,7 @@
     }
 
     print_packet( p, why );
-    if( ( ret = mbedtls_net_send( &dst, p->buf, p->len ) ) <= 0 )
+    if( ( ret = mbedtls_net_send( dst, p->buf, p->len ) ) <= 0 )
     {
         mbedtls_printf( "  ! mbedtls_net_send returned %d\n", ret );
         return( ret );
@@ -338,7 +344,7 @@
     {
         print_packet( p, "duplicated" );
 
-        if( ( ret = mbedtls_net_send( &dst, p->buf, p->len ) ) <= 0 )
+        if( ( ret = mbedtls_net_send( dst, p->buf, p->len ) ) <= 0 )
         {
             mbedtls_printf( "  ! mbedtls_net_send returned %d\n", ret );
             return( ret );
@@ -392,14 +398,16 @@
     }
 }
 
-int handle_message( const char *way, int dst, int src )
+int handle_message( const char *way,
+                    mbedtls_net_context *dst,
+                    mbedtls_net_context *src )
 {
     int ret;
     packet cur;
     size_t id;
 
     /* receive packet */
-    if( ( ret = mbedtls_net_recv( &src, cur.buf, sizeof( cur.buf ) ) ) <= 0 )
+    if( ( ret = mbedtls_net_recv( src, cur.buf, sizeof( cur.buf ) ) ) <= 0 )
     {
         mbedtls_printf( "  ! mbedtls_net_recv returned %d\n", ret );
         return( ret );
@@ -432,7 +440,7 @@
                strcmp( cur.type, "ApplicationData" ) != 0 &&
                ! ( opt.protect_hvr &&
                    strcmp( cur.type, "HelloVerifyRequest" ) == 0 ) &&
-               prev.dst == 0 &&
+               prev.dst == NULL &&
                cur.len != (size_t) opt.protect_len &&
                dropped[id] < DROP_MAX &&
                rand() % opt.delay == 0 ) )
@@ -446,7 +454,7 @@
             return( ret );
 
         /* send previously delayed message if any */
-        if( prev.dst != 0 )
+        if( prev.dst != NULL )
         {
             ret = send_packet( &prev, "delayed" );
             memset( &prev, 0, sizeof( packet ) );
@@ -462,13 +470,15 @@
 {
     int ret;
 
-    int listen_fd = -1;
-    int client_fd = -1;
-    int server_fd = -1;
+    mbedtls_net_context listen_fd, client_fd, server_fd;
 
     int nb_fds;
     fd_set read_fds;
 
+    mbedtls_net_init( &listen_fd );
+    mbedtls_net_init( &client_fd );
+    mbedtls_net_init( &server_fd );
+
     get_options( argc, argv );
 
     /*
@@ -526,7 +536,7 @@
     mbedtls_printf( "  . Waiting for a remote connection ..." );
     fflush( stdout );
 
-    if( ( ret = mbedtls_net_accept( listen_fd, &client_fd,
+    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 );
@@ -555,19 +565,19 @@
     clear_pending();
     memset( dropped, 0, sizeof( dropped ) );
 
-    nb_fds = client_fd;
-    if( nb_fds < server_fd )
-        nb_fds = server_fd;
-    if( nb_fds < listen_fd )
-        nb_fds = listen_fd;
+    nb_fds = client_fd.fd;
+    if( nb_fds < server_fd.fd )
+        nb_fds = server_fd.fd;
+    if( nb_fds < listen_fd.fd )
+        nb_fds = listen_fd.fd;
     ++nb_fds;
 
     while( 1 )
     {
         FD_ZERO( &read_fds );
-        FD_SET( server_fd, &read_fds );
-        FD_SET( client_fd, &read_fds );
-        FD_SET( listen_fd, &read_fds );
+        FD_SET( server_fd.fd, &read_fds );
+        FD_SET( client_fd.fd, &read_fds );
+        FD_SET( listen_fd.fd, &read_fds );
 
         if( ( ret = select( nb_fds, &read_fds, NULL, NULL, NULL ) ) <= 0 )
         {
@@ -575,20 +585,20 @@
             goto exit;
         }
 
-        if( FD_ISSET( listen_fd, &read_fds ) )
+        if( FD_ISSET( listen_fd.fd, &read_fds ) )
             goto accept;
 
-        if( FD_ISSET( client_fd, &read_fds ) )
+        if( FD_ISSET( client_fd.fd, &read_fds ) )
         {
             if( ( ret = handle_message( "S <- C",
-                                        server_fd, client_fd ) ) != 0 )
+                                        &server_fd, &client_fd ) ) != 0 )
                 goto accept;
         }
 
-        if( FD_ISSET( server_fd, &read_fds ) )
+        if( FD_ISSET( server_fd.fd, &read_fds ) )
         {
             if( ( ret = handle_message( "S -> C",
-                                        client_fd, server_fd ) ) != 0 )
+                                        &client_fd, &server_fd ) ) != 0 )
                 goto accept;
         }
     }
@@ -605,11 +615,9 @@
     }
 #endif
 
-    if( client_fd != -1 )
-        mbedtls_net_close( client_fd );
-
-    if( listen_fd != -1 )
-        mbedtls_net_close( listen_fd );
+    mbedtls_net_close( &client_fd );
+    mbedtls_net_close( &server_fd );
+    mbedtls_net_close( &listen_fd );
 
 #if defined(_WIN32)
     mbedtls_printf( "  Press Enter to exit this program.\n" );
diff --git a/programs/x509/cert_app.c b/programs/x509/cert_app.c
index dd39805..dd5c508 100644
--- a/programs/x509/cert_app.c
+++ b/programs/x509/cert_app.c
@@ -142,7 +142,8 @@
 
 int main( int argc, char *argv[] )
 {
-    int ret = 0, server_fd;
+    int ret = 0;
+    mbedtls_net_context server_fd;
     unsigned char buf[1024];
     mbedtls_entropy_context entropy;
     mbedtls_ctr_drbg_context ctr_drbg;
@@ -161,7 +162,7 @@
     /*
      * Set to sane values
      */
-    server_fd = 0;
+    mbedtls_net_init( &server_fd );
     mbedtls_ctr_drbg_init( &ctr_drbg );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
@@ -474,8 +475,7 @@
 
 exit:
 
-    if( server_fd )
-        mbedtls_net_close( server_fd );
+    mbedtls_net_close( &server_fd );
     mbedtls_x509_crt_free( &cacert );
     mbedtls_x509_crt_free( &clicert );
 #if defined(MBEDTLS_X509_CRL_PARSE_C)