diff --git a/CHANGELOG b/CHANGELOG
index ae69d00f..566c33bf 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -6,6 +6,9 @@ HISTORY
 
   ++ New features:
 
+  2017-03-02: Simon Goldschmidt
+  * netconn: added nonblocking accept/recv to netconn API (task #14396)
+
   2017-02-28: Simon Goldschmidt
   * Added LWIP_SINGLE_NETIF for small targets with only one netif
 
diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index e929e532..5f4216bc 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -413,16 +413,25 @@ netconn_accept(struct netconn *conn, struct netconn **new_conn)
   API_MSG_VAR_ALLOC(msg);
 #endif /* TCP_LISTEN_BACKLOG */
 
-#if LWIP_SO_RCVTIMEO
-  if (sys_arch_mbox_fetch(&conn->acceptmbox, &accept_ptr, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
+  if (netconn_is_nonblocking(conn)) {
+    if (sys_arch_mbox_tryfetch(&conn->acceptmbox, &accept_ptr) == SYS_ARCH_TIMEOUT) {
 #if TCP_LISTEN_BACKLOG
-    API_MSG_VAR_FREE(msg);
+      API_MSG_VAR_FREE(msg);
 #endif /* TCP_LISTEN_BACKLOG */
-    return ERR_TIMEOUT;
-  }
+      return ERR_WOULDBLOCK;
+    }
+  } else {
+#if LWIP_SO_RCVTIMEO
+    if (sys_arch_mbox_fetch(&conn->acceptmbox, &accept_ptr, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
+#if TCP_LISTEN_BACKLOG
+      API_MSG_VAR_FREE(msg);
+#endif /* TCP_LISTEN_BACKLOG */
+      return ERR_TIMEOUT;
+    }
 #else
-  sys_arch_mbox_fetch(&conn->acceptmbox, &accept_ptr, 0);
+    sys_arch_mbox_fetch(&conn->acceptmbox, &accept_ptr, 0);
 #endif /* LWIP_SO_RCVTIMEO*/
+  }
   newconn = (struct netconn *)accept_ptr;
   /* Register event with callback */
   API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);
@@ -467,15 +476,21 @@ netconn_accept(struct netconn *conn, struct netconn **new_conn)
 /**
  * @ingroup netconn_common
  * Receive data: actual implementation that doesn't care whether pbuf or netbuf
- * is received
+ * is received (this is internal, it's just here for describing common errors)
  *
  * @param conn the netconn from which to receive data
  * @param new_buf pointer where a new pbuf/netbuf is stored when received data
+ * @param apiflags flags that control function behaviour. For now only:
+ * - NETCONN_DONTBLOCK: only read data that is available now, don't wait for more data
  * @return ERR_OK if data has been received, an error code otherwise (timeout,
  *                memory error or another error)
+ *         ERR_CONN if not connected
+ *         ERR_CLSD if TCP connection has been closed
+ *         ERR_WOULDBLOCK if the netconn is nonblocking but would block to wait for data
+ *         ERR_TIMEOUT if the netconn has a receive timeout and no data was received
  */
 static err_t
-netconn_recv_data(struct netconn *conn, void **new_buf)
+netconn_recv_data(struct netconn *conn, void **new_buf, u8_t apiflags)
 {
   void *buf = NULL;
   u16_t len;
@@ -520,21 +535,35 @@ netconn_recv_data(struct netconn *conn, void **new_buf)
   }
 #endif /* LWIP_TCP */
 
-#if LWIP_SO_RCVTIMEO
-  if (sys_arch_mbox_fetch(&conn->recvmbox, &buf, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
+  if (netconn_is_nonblocking(conn) || (apiflags & NETCONN_DONTBLOCK)) {
+    if (sys_arch_mbox_tryfetch(&conn->recvmbox, &buf) == SYS_ARCH_TIMEOUT) {
 #if LWIP_TCP
 #if (LWIP_UDP || LWIP_RAW)
-    if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
+      if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
 #endif /* (LWIP_UDP || LWIP_RAW) */
-    {
-      API_MSG_VAR_FREE(msg);
-    }
+      {
+        API_MSG_VAR_FREE(msg);
+     }
 #endif /* LWIP_TCP */
-    return ERR_TIMEOUT;
-  }
+     return ERR_WOULDBLOCK;
+    }
+  } else {
+#if LWIP_SO_RCVTIMEO
+    if (sys_arch_mbox_fetch(&conn->recvmbox, &buf, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
+#if LWIP_TCP
+#if (LWIP_UDP || LWIP_RAW)
+      if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
+#endif /* (LWIP_UDP || LWIP_RAW) */
+      {
+        API_MSG_VAR_FREE(msg);
+      }
+#endif /* LWIP_TCP */
+      return ERR_TIMEOUT;
+    }
 #else
-  sys_arch_mbox_fetch(&conn->recvmbox, &buf, 0);
+    sys_arch_mbox_fetch(&conn->recvmbox, &buf, 0);
 #endif /* LWIP_SO_RCVTIMEO*/
+  }
 
 #if LWIP_TCP
 #if (LWIP_UDP || LWIP_RAW)
@@ -600,7 +629,7 @@ netconn_recv_data(struct netconn *conn, void **new_buf)
  * @param conn the netconn from which to receive data
  * @param new_buf pointer where a new pbuf is stored when received data
  * @return ERR_OK if data has been received, an error code otherwise (timeout,
- *                memory error or another error)
+ *                memory error or another error, @see netconn_recv_data)
  *         ERR_ARG if conn is not a TCP netconn
  */
 err_t
@@ -609,7 +638,28 @@ netconn_recv_tcp_pbuf(struct netconn *conn, struct pbuf **new_buf)
   LWIP_ERROR("netconn_recv_tcp_pbuf: invalid conn", (conn != NULL) &&
              NETCONNTYPE_GROUP(netconn_type(conn)) == NETCONN_TCP, return ERR_ARG;);
 
-  return netconn_recv_data(conn, (void **)new_buf);
+  return netconn_recv_data(conn, (void **)new_buf, 0);
+}
+
+/**
+ * @ingroup netconn_tcp
+ * Receive data (in form of a pbuf) from a TCP netconn
+ *
+ * @param conn the netconn from which to receive data
+ * @param new_buf pointer where a new pbuf is stored when received data
+ * @param apiflags flags that control function behaviour. For now only:
+ * - NETCONN_DONTBLOCK: only read data that is available now, don't wait for more data
+ * @return ERR_OK if data has been received, an error code otherwise (timeout,
+ *                memory error or another error, @see netconn_recv_data)
+ *         ERR_ARG if conn is not a TCP netconn
+ */
+err_t
+netconn_recv_tcp_pbuf_flags(struct netconn *conn, struct pbuf **new_buf, u8_t apiflags)
+{
+  LWIP_ERROR("netconn_recv_tcp_pbuf: invalid conn", (conn != NULL) &&
+             NETCONNTYPE_GROUP(netconn_type(conn)) == NETCONN_TCP, return ERR_ARG;);
+
+  return netconn_recv_data(conn, (void **)new_buf, apiflags);
 }
 
 /**
@@ -627,7 +677,27 @@ netconn_recv_udp_raw_netbuf(struct netconn *conn, struct netbuf **new_buf)
   LWIP_ERROR("netconn_recv_udp_raw_netbuf: invalid conn", (conn != NULL) &&
              NETCONNTYPE_GROUP(netconn_type(conn)) != NETCONN_TCP, return ERR_ARG;);
 
-  return netconn_recv_data(conn, (void **)new_buf);
+  return netconn_recv_data(conn, (void **)new_buf, 0);
+}
+
+/**
+ * Receive data (in form of a netbuf) from a UDP or RAW netconn
+ *
+ * @param conn the netconn from which to receive data
+ * @param new_buf pointer where a new netbuf is stored when received data
+ * @param apiflags flags that control function behaviour. For now only:
+ * - NETCONN_DONTBLOCK: only read data that is available now, don't wait for more data
+ * @return ERR_OK if data has been received, an error code otherwise (timeout,
+ *                memory error or another error)
+ *         ERR_ARG if conn is not a UDP/RAW netconn
+ */
+err_t
+netconn_recv_udp_raw_netbuf_flags(struct netconn *conn, struct netbuf **new_buf, u8_t apiflags)
+{
+  LWIP_ERROR("netconn_recv_udp_raw_netbuf: invalid conn", (conn != NULL) &&
+             NETCONNTYPE_GROUP(netconn_type(conn)) != NETCONN_TCP, return ERR_ARG;);
+
+  return netconn_recv_data(conn, (void **)new_buf, apiflags);
 }
 
 /**
@@ -664,7 +734,7 @@ netconn_recv(struct netconn *conn, struct netbuf **new_buf)
       return ERR_MEM;
     }
 
-    err = netconn_recv_data(conn, (void **)&p);
+    err = netconn_recv_data(conn, (void **)&p, 0);
     if (err != ERR_OK) {
       memp_free(MEMP_NETBUF, buf);
       return err;
@@ -685,7 +755,7 @@ netconn_recv(struct netconn *conn, struct netbuf **new_buf)
 #endif /* LWIP_TCP && (LWIP_UDP || LWIP_RAW) */
   {
 #if (LWIP_UDP || LWIP_RAW)
-    return netconn_recv_data(conn, (void **)new_buf);
+    return netconn_recv_data(conn, (void **)new_buf, 0);
 #endif /* (LWIP_UDP || LWIP_RAW) */
   }
 }
diff --git a/src/include/lwip/api.h b/src/include/lwip/api.h
index 23aa774e..2510d403 100644
--- a/src/include/lwip/api.h
+++ b/src/include/lwip/api.h
@@ -311,7 +311,9 @@ err_t   netconn_listen_with_backlog(struct netconn *conn, u8_t backlog);
 err_t   netconn_accept(struct netconn *conn, struct netconn **new_conn);
 err_t   netconn_recv(struct netconn *conn, struct netbuf **new_buf);
 err_t   netconn_recv_udp_raw_netbuf(struct netconn *conn, struct netbuf **new_buf);
+err_t   netconn_recv_udp_raw_netbuf_flags(struct netconn *conn, struct netbuf **new_buf, u8_t apiflags);
 err_t   netconn_recv_tcp_pbuf(struct netconn *conn, struct pbuf **new_buf);
+err_t   netconn_recv_tcp_pbuf_flags(struct netconn *conn, struct pbuf **new_buf, u8_t apiflags);
 err_t   netconn_sendto(struct netconn *conn, struct netbuf *buf,
                              const ip_addr_t *addr, u16_t port);
 err_t   netconn_send(struct netconn *conn, struct netbuf *buf);