diff --git a/unix/fdfile.h b/unix/fdfile.h
new file mode 100644
index 0000000000..8e8e97c795
--- /dev/null
+++ b/unix/fdfile.h
@@ -0,0 +1,41 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013, 2014 Damien P. George
+ * Copyright (c) 2016 Paul Sokolovsky
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/obj.h"
+
+#ifndef __MICROPY_INCLUDED_UNIX_FILE_H__
+#define __MICROPY_INCLUDED_UNIX_FILE_H__
+
+typedef struct _mp_obj_fdfile_t {
+    mp_obj_base_t base;
+    int fd;
+} mp_obj_fdfile_t;
+
+extern const mp_obj_type_t mp_type_fileio;
+extern const mp_obj_type_t mp_type_textio;
+
+#endif // __MICROPY_INCLUDED_UNIX_FILE_H__
diff --git a/unix/file.c b/unix/file.c
index 2236328576..203a5a3abe 100644
--- a/unix/file.c
+++ b/unix/file.c
@@ -36,6 +36,7 @@
 #include "py/stream.h"
 #include "py/builtin.h"
 #include "py/mphal.h"
+#include "fdfile.h"
 
 #if MICROPY_PY_IO
 
@@ -43,11 +44,6 @@
 #define fsync _commit
 #endif
 
-typedef struct _mp_obj_fdfile_t {
-    mp_obj_base_t base;
-    int fd;
-} mp_obj_fdfile_t;
-
 #ifdef MICROPY_CPYTHON_COMPAT
 STATIC void check_fd_is_open(const mp_obj_fdfile_t *o) {
     if (o->fd < 0) {
diff --git a/unix/modsocket.c b/unix/modsocket.c
index cd68b20a45..56bab3494a 100644
--- a/unix/modsocket.c
+++ b/unix/modsocket.c
@@ -62,12 +62,14 @@
 
 #define MICROPY_SOCKET_EXTRA (0)
 
+// This type must "inherit" from mp_obj_fdfile_t, i.e. matching subset of
+// fields should have the same layout.
 typedef struct _mp_obj_socket_t {
     mp_obj_base_t base;
     int fd;
 } mp_obj_socket_t;
 
-STATIC const mp_obj_type_t usocket_type;
+const mp_obj_type_t mp_type_socket;
 
 // Helper functions
 #define RAISE_ERRNO(err_flag, error_val) \
@@ -80,7 +82,7 @@ static inline mp_obj_t mp_obj_from_sockaddr(const struct sockaddr *addr, socklen
 
 STATIC mp_obj_socket_t *socket_new(int fd) {
     mp_obj_socket_t *o = m_new_obj(mp_obj_socket_t);
-    o->base.type = &usocket_type;
+    o->base.type = &mp_type_socket;
     o->fd = fd;
     return o;
 }
@@ -374,7 +376,7 @@ STATIC const mp_stream_p_t usocket_stream_p = {
     .write = socket_write,
 };
 
-STATIC const mp_obj_type_t usocket_type = {
+const mp_obj_type_t mp_type_socket = {
     { &mp_type_type },
     .name = MP_QSTR_socket,
     .print = socket_print,
@@ -550,7 +552,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_socket_sockaddr_obj, mod_socket_sockaddr);
 
 STATIC const mp_rom_map_elem_t mp_module_socket_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_usocket) },
-    { MP_ROM_QSTR(MP_QSTR_socket), MP_ROM_PTR(&usocket_type) },
+    { MP_ROM_QSTR(MP_QSTR_socket), MP_ROM_PTR(&mp_type_socket) },
     { MP_ROM_QSTR(MP_QSTR_getaddrinfo), MP_ROM_PTR(&mod_socket_getaddrinfo_obj) },
     { MP_ROM_QSTR(MP_QSTR_inet_pton), MP_ROM_PTR(&mod_socket_inet_pton_obj) },
     { MP_ROM_QSTR(MP_QSTR_inet_ntop), MP_ROM_PTR(&mod_socket_inet_ntop_obj) },
diff --git a/unix/moduselect.c b/unix/moduselect.c
index 13cb3f1fa8..38f8d11ed8 100644
--- a/unix/moduselect.c
+++ b/unix/moduselect.c
@@ -38,6 +38,9 @@
 #include "py/objlist.h"
 #include "py/objtuple.h"
 #include "py/mphal.h"
+#include "fdfile.h"
+
+extern const mp_obj_type_t mp_type_socket;
 
 // Flags for poll()
 #define FLAG_ONESHOT (1)
@@ -51,10 +54,23 @@ typedef struct _mp_obj_poll_t {
     struct pollfd *entries;
 } mp_obj_poll_t;
 
+STATIC int get_fd(mp_obj_t fdlike) {
+    int fd;
+    // Shortcut for fdfile compatible types
+    if (MP_OBJ_IS_TYPE(fdlike, &mp_type_fileio) || MP_OBJ_IS_TYPE(fdlike, &mp_type_socket)) {
+        mp_obj_fdfile_t *fdfile = MP_OBJ_TO_PTR(fdlike);
+        fd = fdfile->fd;
+    } else {
+        fd = mp_obj_get_int(fdlike);
+    }
+    return fd;
+}
+
 /// \method register(obj[, eventmask])
 STATIC mp_obj_t poll_register(size_t n_args, const mp_obj_t *args) {
     mp_obj_poll_t *self = MP_OBJ_TO_PTR(args[0]);
-    int fd = mp_obj_get_int(args[1]);
+    int fd = get_fd(args[1]);
+
     mp_uint_t flags;
     if (n_args == 3) {
         flags = mp_obj_get_int(args[2]);
@@ -95,7 +111,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(poll_register_obj, 2, 3, poll_register);
 STATIC mp_obj_t poll_unregister(mp_obj_t self_in, mp_obj_t obj_in) {
     mp_obj_poll_t *self = MP_OBJ_TO_PTR(self_in);
     struct pollfd *entries = self->entries;
-    int fd = mp_obj_get_int(obj_in);
+    int fd = get_fd(obj_in);
     for (int i = self->len - 1; i >= 0; i--) {
         if (entries->fd == fd) {
             entries->fd = -1;
@@ -113,7 +129,7 @@ MP_DEFINE_CONST_FUN_OBJ_2(poll_unregister_obj, poll_unregister);
 STATIC mp_obj_t poll_modify(mp_obj_t self_in, mp_obj_t obj_in, mp_obj_t eventmask_in) {
     mp_obj_poll_t *self = MP_OBJ_TO_PTR(self_in);
     struct pollfd *entries = self->entries;
-    int fd = mp_obj_get_int(obj_in);
+    int fd = get_fd(obj_in);
     for (int i = self->len - 1; i >= 0; i--) {
         if (entries->fd == fd) {
             entries->events = mp_obj_get_int(eventmask_in);