diff --git a/lib/libwebsockets.h b/lib/libwebsockets.h
index 3c0f185f..3e1db934 100644
--- a/lib/libwebsockets.h
+++ b/lib/libwebsockets.h
@@ -237,26 +237,45 @@ enum libwebsocket_callback_reasons {
 	LWS_CALLBACK_USER = 1000, /* user code can use any including / above */
 };
 
-// argument structure for all external poll related calls
-// passed in via 'in'
-struct libwebsocket_pollargs {
-    int fd;            // applicable file descriptor
-    int events;        // the new event mask
-    int prev_events;   // the previous event mask
-};
 
-
-#if defined(_WIN32) && (_WIN32_WINNT < 0x0600)	
+#if defined(_WIN32) && (_WIN32_WINNT < 0x0600)
+typedef SOCKET lws_sockfd_type;
 struct libwebsocket_pollfd {
-	SOCKET fd;
+	lws_sockfd_type fd;
 	SHORT events;
 	SHORT revents;
 };
 WINSOCK_API_LINKAGE int WSAAPI WSAPoll(struct libwebsocket_pollfd fdArray[], ULONG fds, INT timeout);
 #else
+
+#if defined(MBED_OPERATORS)
+typedef int lws_sockfd_type;
+struct pollfd {
+	lws_sockfd_type *fd;
+	short events;
+	short revents;
+};
+#define POLLIN          0x0001
+#define POLLPRI         0x0002
+#define POLLOUT         0x0004
+#define POLLERR         0x0008
+#define POLLHUP         0x0010
+#define POLLNVAL        0x0020
+#else
+typedef int lws_fd_type;
+#endif
+
 #define libwebsocket_pollfd pollfd
 #endif
 
+// argument structure for all external poll related calls
+// passed in via 'in'
+struct libwebsocket_pollargs {
+    lws_sockfd_type fd;            // applicable file descriptor
+    int events;        // the new event mask
+    int prev_events;   // the previous event mask
+};
+
 enum libwebsocket_extension_callback_reasons {
 	LWS_EXT_CALLBACK_SERVER_CONTEXT_CONSTRUCT,
 	LWS_EXT_CALLBACK_CLIENT_CONTEXT_CONSTRUCT,
@@ -1356,7 +1375,7 @@ libwebsocket_canonical_hostname(struct libwebsocket_context *context);
 
 LWS_VISIBLE LWS_EXTERN void
 libwebsockets_get_peer_addresses(struct libwebsocket_context *context,
-		struct libwebsocket *wsi, int fd, char *name, int name_len,
+		struct libwebsocket *wsi, lws_sockfd_type fd, char *name, int name_len,
 					char *rip, int rip_len);
 
 LWS_VISIBLE LWS_EXTERN int
diff --git a/lib/private-libwebsockets.h b/lib/private-libwebsockets.h
index 5b1238e3..ece8380e 100644
--- a/lib/private-libwebsockets.h
+++ b/lib/private-libwebsockets.h
@@ -477,7 +477,7 @@ struct libwebsocket_context {
 	int fd_random;
 	int listen_service_modulo;
 	int listen_service_count;
-	int listen_service_fd;
+	lws_sockfd_type listen_service_fd;
 	int listen_service_extraseen;
 
 	/*
@@ -532,7 +532,7 @@ enum {
 LWS_EXTERN void lws_feature_status_libev(struct lws_context_creation_info *info);
 LWS_EXTERN void
 lws_libev_accept(struct libwebsocket_context *context,
-		 struct libwebsocket *new_wsi, int accept_fd);
+		 struct libwebsocket *new_wsi, lws_sockfd_type accept_fd);
 LWS_EXTERN void
 lws_libev_io(struct libwebsocket_context *context,
 				struct libwebsocket *wsi, int flags);
@@ -612,7 +612,7 @@ struct _lws_http_mode_related {
 #if defined(WIN32) || defined(_WIN32)
 	HANDLE fd;
 #else
-	int fd;
+	lws_sockfd_type fd;
 #endif
 	unsigned long filepos;
 	unsigned long filelen;
@@ -842,7 +842,7 @@ struct libwebsocket {
 
 	char pending_timeout; /* enum pending_timeout */
 	time_t pending_timeout_limit;
-	int sock;
+	lws_sockfd_type sock;
 	int position_in_fds_table;
 #ifdef LWS_LATENCY
 	unsigned long action_start;
@@ -930,13 +930,13 @@ lws_b64_selftest(void);
 
 #ifdef _WIN32
 LWS_EXTERN struct libwebsocket *
-wsi_from_fd(struct libwebsocket_context *context, int fd);
+wsi_from_fd(struct libwebsocket_context *context, lws_sockfd_type fd);
 
 LWS_EXTERN int 
 insert_wsi(struct libwebsocket_context *context, struct libwebsocket *wsi);
 
 LWS_EXTERN int
-delete_from_fd(struct libwebsocket_context *context, int fd);
+delete_from_fd(struct libwebsocket_context *context, lws_sockfd_type fd);
 #else
 #define wsi_from_fd(A,B)  A->lws_lookup[B] 
 #define insert_wsi(A,B)   A->lws_lookup[B->sock]=B
@@ -1067,7 +1067,7 @@ void lws_http2_configure_if_upgraded(struct libwebsocket *wsi);
 #endif
 
 LWS_EXTERN int
-lws_plat_set_socket_options(struct libwebsocket_context *context, int fd);
+lws_plat_set_socket_options(struct libwebsocket_context *context, lws_sockfd_type fd);
 
 LWS_EXTERN int
 lws_allocate_header_table(struct libwebsocket *wsi);
@@ -1152,7 +1152,7 @@ lws_ssl_pending(struct libwebsocket *wsi);
 LWS_EXTERN int
 lws_server_socket_service_ssl(struct libwebsocket_context *context,
 		struct libwebsocket **wsi, struct libwebsocket *new_wsi,
-		int accept_fd, struct libwebsocket_pollfd *pollfd);
+		lws_sockfd_type accept_fd, struct libwebsocket_pollfd *pollfd);
 LWS_EXTERN int
 lws_ssl_close(struct libwebsocket *wsi);
 LWS_EXTERN void
diff --git a/lib/server.c b/lib/server.c
index 632a5293..14acf2e7 100644
--- a/lib/server.c
+++ b/lib/server.c
@@ -26,7 +26,7 @@ int lws_context_init_server(struct lws_context_creation_info *info,
 			    struct libwebsocket_context *context)
 {
 	int n;
-	int sockfd;
+	lws_sockfd_type sockfd;
 	struct sockaddr_in sin;
 	socklen_t len = sizeof(sin);
 	int opt = 1;