diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index e03b8b74..8c934f8a 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -94,8 +94,13 @@
 #if LWIP_NETCONN_FULLDUPLEX
 #define NETCONN_RECVMBOX_WAITABLE(conn) (sys_mbox_valid(&(conn)->recvmbox) && (((conn)->flags & NETCONN_FLAG_MBOXINVALID) == 0))
 #define NETCONN_ACCEPTMBOX_WAITABLE(conn) (sys_mbox_valid(&(conn)->acceptmbox) && (((conn)->flags & (NETCONN_FLAG_MBOXCLOSED|NETCONN_FLAG_MBOXINVALID)) == 0))
+#if ESP_LWIP_LOCK
+#define NETCONN_MBOX_WAITING_INC(conn) conn->mbox_threads_waiting += 1
+#define NETCONN_MBOX_WAITING_DEC(conn) conn->mbox_threads_waiting -= 1
+#else 
 #define NETCONN_MBOX_WAITING_INC(conn) SYS_ARCH_INC(conn->mbox_threads_waiting, 1)
 #define NETCONN_MBOX_WAITING_DEC(conn) SYS_ARCH_DEC(conn->mbox_threads_waiting, 1)
+#endif /* ESP_LWIP_LOCK */
 #else /* LWIP_NETCONN_FULLDUPLEX */
 #define NETCONN_RECVMBOX_WAITABLE(conn)   sys_mbox_valid(&(conn)->recvmbox)
 #define NETCONN_ACCEPTMBOX_WAITABLE(conn) (sys_mbox_valid(&(conn)->acceptmbox) && (((conn)->flags & NETCONN_FLAG_MBOXCLOSED) == 0))
@@ -585,8 +590,14 @@ netconn_recv_data(struct netconn *conn, void **new_buf, u8_t apiflags)
   *new_buf = NULL;
   LWIP_ERROR("netconn_recv: invalid conn",    (conn != NULL),    return ERR_ARG;);
 
+#if ESP_LWIP_LOCK
+  NETCONN_MBOX_WAITING_INC(conn);
+#endif /* ESP_LWIP_LOCK */
   if (!NETCONN_RECVMBOX_WAITABLE(conn)) {
     err_t err = netconn_err(conn);
+#if ESP_LWIP_LOCK
+    NETCONN_MBOX_WAITING_DEC(conn);
+#endif /* ESP_LWIP_LOCK */   
     if (err != ERR_OK) {
       /* return pending error */
       return err;
@@ -594,7 +605,9 @@ netconn_recv_data(struct netconn *conn, void **new_buf, u8_t apiflags)
     return ERR_CONN;
   }
 
+#if !ESP_LWIP_LOCK
   NETCONN_MBOX_WAITING_INC(conn);
+#endif /* !ESP_LWIP_LOCK */  
   if (netconn_is_nonblocking(conn) || (apiflags & NETCONN_DONTBLOCK) ||
       (conn->flags & NETCONN_FLAG_MBOXCLOSED) || (conn->pending_err != ERR_OK)) {
     if (sys_arch_mbox_tryfetch(&conn->recvmbox, &buf) == SYS_ARCH_TIMEOUT) {
diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index 44836a74..a17f32c5 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -922,8 +922,11 @@ netconn_mark_mbox_invalid(struct netconn *conn)
 
   /* Prevent new calls/threads from reading from the mbox */
   conn->flags |= NETCONN_FLAG_MBOXINVALID;
-
+#if ESP_LWIP_LOCK
   SYS_ARCH_LOCKED(num_waiting = conn->mbox_threads_waiting);
+#else
+  num_waiting = conn->mbox_threads_waiting;
+#endif /* ESP_LWIP_LOCK */  
   for (i = 0; i < num_waiting; i++) {
     if (sys_mbox_valid_val(conn->recvmbox)) {
       sys_mbox_trypost(&conn->recvmbox, msg);
diff --git a/src/api/sockets.c b/src/api/sockets.c
index 79121945..b7ec022f 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -289,7 +289,11 @@ static struct lwip_select_cb *select_cb_list;
 #if LWIP_SOCKET_SELECT || LWIP_SOCKET_POLL
 static void event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len);
 #define DEFAULT_SOCKET_EVENTCB event_callback
+#if ESP_LWIP_SELECT
+static void select_check_waiters(int s, int has_recvevent, int has_sendevent, int has_errevent, struct lwip_sock *sock_select);
+#else
 static void select_check_waiters(int s, int has_recvevent, int has_sendevent, int has_errevent);
+#endif /* LWIP_SOCKET_SELECT */
 #else
 #define DEFAULT_SOCKET_EVENTCB NULL
 #endif
@@ -337,11 +341,17 @@ static int
 sock_inc_used(struct lwip_sock *sock)
 {
   int ret;
+#if !ESP_LWIP_LOCK
   SYS_ARCH_DECL_PROTECT(lev);
+#endif /* !ESP_LWIP_LOCK */  
 
   LWIP_ASSERT("sock != NULL", sock != NULL);
 
+#if ESP_LWIP_LOCK
+  SYS_ARCH_PROTECT_SOCK(sock);
+#else
   SYS_ARCH_PROTECT(lev);
+#endif /* ESP_LWIP_LOCK */
   if (sock->fd_free_pending) {
     /* prevent new usage of this socket if free is pending */
     ret = 0;
@@ -350,7 +360,11 @@ sock_inc_used(struct lwip_sock *sock)
     ret = 1;
     LWIP_ASSERT("sock->fd_used != 0", sock->fd_used != 0);
   }
+#if ESP_LWIP_LOCK
+  SYS_ARCH_UNPROTECT_SOCK(sock);
+#else 
   SYS_ARCH_UNPROTECT(lev);
+#endif /* ESP_LWIP_LOCK */  
   return ret;
 }
 
@@ -360,13 +374,22 @@ sock_inc_used_locked(struct lwip_sock *sock)
 {
   LWIP_ASSERT("sock != NULL", sock != NULL);
 
+#if ESP_LWIP_LOCK
+  SYS_ARCH_PROTECT_SOCK(sock);
+#endif /* ESP_LWIP_LOCK */  
   if (sock->fd_free_pending) {
     LWIP_ASSERT("sock->fd_used != 0", sock->fd_used != 0);
+#if ESP_LWIP_LOCK
+  SYS_ARCH_UNPROTECT_SOCK(sock);
+#endif /* ESP_LWIP_LOCK */
     return 0;
   }
 
   ++sock->fd_used;
   LWIP_ASSERT("sock->fd_used != 0", sock->fd_used != 0);
+#if ESP_LWIP_LOCK
+  SYS_ARCH_UNPROTECT_SOCK(sock);
+#endif /* ESP_LWIP_LOCK */ 
   return 1;
 }
 
@@ -382,10 +405,16 @@ done_socket(struct lwip_sock *sock)
   int is_tcp = 0;
   struct netconn *conn = NULL;
   union lwip_sock_lastdata lastdata;
+#if !ESP_LWIP_LOCK
   SYS_ARCH_DECL_PROTECT(lev);
+#endif /* !ESP_LWIP_LOCK */ 
   LWIP_ASSERT("sock != NULL", sock != NULL);
 
+#if ESP_LWIP_LOCK
+  SYS_ARCH_PROTECT_SOCK(sock);
+#else
   SYS_ARCH_PROTECT(lev);
+#endif /* ESP_LWIP_LOCK */
   LWIP_ASSERT("sock->fd_used > 0", sock->fd_used > 0);
   if (--sock->fd_used == 0) {
     if (sock->fd_free_pending) {
@@ -395,7 +424,11 @@ done_socket(struct lwip_sock *sock)
       freed = free_socket_locked(sock, is_tcp, &conn, &lastdata);
     }
   }
+#if ESP_LWIP_LOCK
+  SYS_ARCH_UNPROTECT_SOCK(sock);
+#else 
   SYS_ARCH_UNPROTECT(lev);
+#endif /* ESP_LWIP_LOCK */
 
   if (freed) {
     free_socket_free_elements(is_tcp, conn, &lastdata);
@@ -536,6 +569,14 @@ alloc_socket(struct netconn *newconn, int accepted)
       sockets[i].sendevent  = (NETCONNTYPE_GROUP(newconn->type) == NETCONN_TCP ? (accepted != 0) : 1);
       sockets[i].errevent   = 0;
 #endif /* LWIP_SOCKET_SELECT || LWIP_SOCKET_POLL */
+#if ESP_LWIP_LOCK
+      if (!sockets[i].lock) {
+        /* one time init and never free */
+        if (sys_mutex_new(&sockets[i].lock) != ERR_OK) {
+          return -1;
+        }
+      }
+#endif
       return i + LWIP_SOCKET_OFFSET;
     }
     SYS_ARCH_UNPROTECT(lev);
@@ -602,13 +643,23 @@ free_socket(struct lwip_sock *sock, int is_tcp)
   int freed;
   struct netconn *conn;
   union lwip_sock_lastdata lastdata;
+#if !ESP_LWIP_LOCK
   SYS_ARCH_DECL_PROTECT(lev);
+#endif /* !ESP_LWIP_LOCK */
 
   /* Protect socket array */
+#if ESP_LWIP_LOCK
+  SYS_ARCH_PROTECT_SOCK(sock);
+#else
   SYS_ARCH_PROTECT(lev);
+#endif /* ESP_LWIP_LOCK */
 
   freed = free_socket_locked(sock, is_tcp, &conn, &lastdata);
+#if ESP_LWIP_LOCK
+  SYS_ARCH_UNPROTECT_SOCK(sock);
+#else 
   SYS_ARCH_UNPROTECT(lev);
+#endif /* ESP_LWIP_LOCK */
   /* don't use 'sock' after this line, as another task might have allocated it */
 
   if (freed) {
@@ -2509,8 +2560,11 @@ event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len)
       s = conn->socket;
       SYS_ARCH_UNPROTECT(lev);
     }
-
+#if ESP_LWIP_LOCK
+    sock = tryget_socket_unconn_nouse(s);
+#else    
     sock = get_socket(s);
+#endif /* ESP_LWIP_LOCK */    
     if (!sock) {
       return;
     }
@@ -2558,11 +2612,17 @@ event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len)
     has_errevent = sock->errevent != 0;
     SYS_ARCH_UNPROTECT(lev);
     /* Check any select calls waiting on this socket */
+#if ESP_LWIP_SELECT
+    select_check_waiters(s, has_recvevent, has_sendevent, has_errevent, sock);
+#else    
     select_check_waiters(s, has_recvevent, has_sendevent, has_errevent);
-  } else {
+#endif/* LWIP_SOCKET_SELECT */   
+  } else {       
     SYS_ARCH_UNPROTECT(lev);
   }
-  done_socket(sock);
+#if !ESP_LWIP_LOCK  
+   done_socket(sock);
+#endif /* !ESP_LWIP_LOCK */  
 }
 
 /**
@@ -2578,19 +2638,24 @@ event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len)
  * select_cb_list during our UNPROTECT/PROTECT. We use a generational counter to
  * detect this change and restart the list walk. The list is expected to be small
  */
+#if ESP_LWIP_SELECT
+static void select_check_waiters(int s, int has_recvevent, int has_sendevent, int has_errevent, struct lwip_sock *sock_select)
+#else
 static void select_check_waiters(int s, int has_recvevent, int has_sendevent, int has_errevent)
+#endif /* LWIP_SOCKET_SELECT */
 {
   struct lwip_select_cb *scb;
-  struct lwip_sock *sock;
+#if ESP_LWIP_SELECT
+  struct lwip_sock *sock = sock_select;
+#else  
+  struct lwip_sock *sock
+#endif /* ESP_LWIP_LOCK */ 
 #if !LWIP_TCPIP_CORE_LOCKING
   int last_select_cb_ctr;
   SYS_ARCH_DECL_PROTECT(lev);
 #endif /* !LWIP_TCPIP_CORE_LOCKING */
 
   LWIP_ASSERT_CORE_LOCKED();
-#if ESP_LWIP_SELECT  
-  sock = tryget_socket_unconn(s);
-#endif/* ESP_LWIP_SELECT */ 
 #if !LWIP_TCPIP_CORE_LOCKING
   SYS_ARCH_PROTECT(lev);
 again:
@@ -2664,9 +2729,6 @@ again:
     last_select_cb_ctr = select_cb_ctr;
   }
   SYS_ARCH_UNPROTECT(lev);
-#if ESP_LWIP_SELECT  
-  done_socket(sock);
-#endif/* ESP_LWIP_SELECT */  
 #endif
 }
 #endif /* LWIP_SOCKET_SELECT || LWIP_SOCKET_POLL */
diff --git a/src/include/lwip/priv/sockets_priv.h b/src/include/lwip/priv/sockets_priv.h
index d8f9904d..48074ee3 100644
--- a/src/include/lwip/priv/sockets_priv.h
+++ b/src/include/lwip/priv/sockets_priv.h
@@ -89,6 +89,11 @@ struct lwip_sock {
 #define LWIP_SOCK_FD_FREE_TCP  1
 #define LWIP_SOCK_FD_FREE_FREE 2
 #endif
+
+#if ESP_LWIP_LOCK
+  sys_mutex_t lock;
+#endif
+
 };
 
 #ifndef set_errno
diff --git a/src/include/lwip/sys.h b/src/include/lwip/sys.h
index 579a750f..705eddbc 100644
--- a/src/include/lwip/sys.h
+++ b/src/include/lwip/sys.h
@@ -83,6 +83,24 @@ typedef u8_t sys_mbox_t;
 
 #else /* NO_SYS */
 
+#if ESP_LWIP_LOCK
+#define SYS_ARCH_PROTECT_CONN(_conn) do {\
+  sys_mutex_lock(&(_conn)->lock);\
+} while(0)
+
+#define SYS_ARCH_UNPROTECT_CONN(_conn) do {\
+  sys_mutex_unlock(&(_conn)->lock);\
+} while(0)
+
+#define SYS_ARCH_PROTECT_SOCK(_sock) do {\
+  sys_mutex_lock(&(_sock)->lock);\
+} while(0)
+
+#define SYS_ARCH_UNPROTECT_SOCK(_sock) do{\
+  sys_mutex_unlock(&(_sock)->lock);\
+} while(0)
+#endif /* ESP_LWIP_LOCK */
+
 /** Return code for timeouts from sys_arch_mbox_fetch and sys_arch_sem_wait */
 #define SYS_ARCH_TIMEOUT 0xffffffffUL
 
diff --git a/test/unit/lwipopts.h b/test/unit/lwipopts.h
index 99299649..af19bb84 100644
--- a/test/unit/lwipopts.h
+++ b/test/unit/lwipopts.h
@@ -100,5 +100,6 @@
 #define ESP_LWIP_MLD6_TIMERS_ONDEMAND           1
 #define ESP_GRATUITOUS_ARP                      1
 #define ESP_LWIP_SELECT                         1
+#define ESP_LWIP_LOCK                           1
 
 #endif /* LWIP_HDR_LWIPOPTS_H */