diff --git a/tulip/selectors.py b/tulip/selectors.py
new file mode 100644
--- /dev/null
+++ b/tulip/selectors.py
@@ -0,0 +1,347 @@
+"""Select module.
+
+This module supports asynchronous I/O on multiple file descriptors.
+"""
+
+
+from select import *    # XXX
+
+
+# generic events, that must be mapped to implementation-specific ones
+# read event
+SELECT_IN  = (1 << 0)
+# write event
+SELECT_OUT = (1 << 1)
+# connect event
+SELECT_CONNECT = SELECT_OUT
+
+
+def _fileobj_to_fd(fileobj):
+    """Return a file descriptor from a file object.
+
+    Parameters:
+    fileobj -- file descriptor, or any object with a `fileno()` method
+
+    Returns:
+    corresponding file descriptor
+    """
+    if isinstance(fileobj, int):
+        fd = fileobj
+    else:
+        try:
+            fd = int(fileobj.fileno())
+        except (ValueError, TypeError):
+            raise ValueError("Invalid file object: {!r}".format(fileobj))
+    return fd
+
+
+class _Key:
+    """Object used internally to associate a file object to its backing file
+    descriptor, selected event mask and attached data."""
+
+    def __init__(self, fileobj, events, data=None):
+        self.fileobj = fileobj
+        self.fd = _fileobj_to_fd(fileobj)
+        self.events = events
+        self.data = data
+
+
+class _BaseSelector:
+    """Base selector class.
+
+    A selector supports registering file objects to be monitored for specific
+    I/O events.
+
+    A file object is a file descriptor or any object with a `fileno()` method.
+    An arbitrary object can be attached to the file object, which can be used
+    for example to store context information, a callback, etc.
+
+    A selector can use various implementations (select(), poll(), epoll()...)
+    depending on the platform. The default `Selector` class uses the most
+    performant implementation on the current platform.
+    """
+
+    def __init__(self):
+        # this maps file descriptors to keys
+        self._fd_to_key = {}
+        # this maps file objects to keys - for fast (un)registering
+        self._fileobj_to_key = {}
+
+    def register(self, fileobj, events, data=None):
+        """Register a file object.
+
+        Parameters:
+        fileobj -- file object
+        events  -- events to monitor (bitwise mask of SELECT_IN|SELECT_OUT)
+        data    -- attached data
+        """
+        if (not events) or (events & ~(SELECT_IN|SELECT_OUT)):
+            raise ValueError("Invalid events: {}".format(events))
+
+        if fileobj in self._fileobj_to_key:
+            raise ValueError("{!r} is already registered".format(fileobj))
+
+        key = _Key(fileobj, events, data)
+        self._fd_to_key[key.fd] = key
+        self._fileobj_to_key[fileobj] = key
+        return key
+
+    def unregister(self, fileobj):
+        """Unregister a file object.
+
+        Parameters:
+        fileobj -- file object
+        """
+        try:
+            key = self._fileobj_to_key[fileobj]
+            del self._fd_to_key[key.fd]
+            del self._fileobj_to_key[fileobj]
+        except KeyError:
+            raise ValueError("{!r} is not registered".format(fileobj))
+        return key
+
+    def modify(self, fileobj, events, data=None):
+        """Change a registered file object monitored events or attached data.
+
+        Parameters:
+        fileobj -- file object
+        events  -- events to monitor (bitwise mask of SELECT_IN|SELECT_OUT)
+        data    -- attached data
+        """
+        self.unregister(fileobj)
+        self.register(fileobj, events, data)
+
+    def select(self, timeout=None):
+        """Perform the actual selection, until some monitored file objects are
+        ready or a timeout expires.
+        
+        Parameters:
+        timeout -- if timeout > 0, this specifies the maximum wait time, in
+                   seconds
+                   if timeout == 0, the select() call won't block, and will
+                   report the currently ready file objects
+                   if timeout is None, select() will block until a monitored
+                   file object becomes ready
+
+        Returns:
+        list of (fileobj, events, attached data) for ready file objects
+        `events` is a bitwise mask of SELECT_IN|SELECT_OUT
+        """
+        raise NotImplementedError()
+
+    def close(self):
+        """Close the selector.
+
+        This must be called to make sure that any underlying resource is freed.
+        """
+        self._fd_to_key.clear()
+        self._fileobj_to_key.clear()
+
+    def get_info(self, fileobj):
+        """Return information about a registered file object.
+
+        Returns:
+        (events, data) associated to this file object
+
+        Raises KeyError if the file object is not registered.
+        """
+        try:
+            key = self._fileobj_to_key[fileobj]
+        except KeyError:
+            raise KeyError("{} is not registered".format(fileobj))
+        return key.events, key.data
+
+    def registered_count(self):
+        """Return the number of registered file objects.
+
+        Returns:
+        number of currently registered file objects
+        """
+        return len(self._fd_to_key)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+    def _key_from_fd(self, fd):
+        """Return the key associated to a given file descriptor.
+
+        Parameters:
+        fd -- file descriptor
+
+        Returns:
+        corresponding key
+        """
+        try:
+            return self._fd_to_key[fd]
+        except KeyError:
+            raise RuntimeError("No key found for fd {}".format(fd))
+
+
+class SelectSelector(_BaseSelector):
+    """Select-based selector."""
+
+    def __init__(self):
+        super().__init__()
+        self._readers = set()
+        self._writers = set()
+
+    def register(self, fileobj, events, data=None):
+        key = super().register(fileobj, events, data)
+        if events & SELECT_IN:
+            self._readers.add(key.fd)
+        if events & SELECT_OUT:
+            self._writers.add(key.fd)
+
+    def unregister(self, fileobj):
+        key = super().unregister(fileobj)
+        self._readers.discard(key.fd)
+        self._writers.discard(key.fd)
+
+    def select(self, timeout=None):
+        r, w, _ = select(self._readers, self._writers, [], timeout)
+        r = set(r)
+        w = set(w)
+        ready = []
+        for fd in r | w:
+            events = 0
+            if fd in r:
+                events |= SELECT_IN
+            if fd in w:
+                events |= SELECT_OUT
+
+            key = self._key_from_fd(fd)
+            ready.append((key.fileobj, events, key.data))
+        return ready
+
+
+if 'poll' in globals():
+
+    class PollSelector(_BaseSelector):
+        """Poll-based selector."""
+    
+        def __init__(self):
+            super().__init__()
+            self._poll = poll()
+    
+        def register(self, fileobj, events, data=None):
+            key = super().register(fileobj, events, data)
+            poll_events = 0
+            if events & SELECT_IN:
+                poll_events |= POLLIN
+            if events & SELECT_OUT:
+                poll_events |= POLLOUT
+            self._poll.register(key.fd, poll_events)
+    
+        def unregister(self, fileobj):
+            key = super().unregister(fileobj)
+            self._poll.unregister(key.fd)
+    
+        def select(self, timeout=None):
+            timeout = None if timeout is None else int(1000 * timeout)
+            ready = []
+            for fd, event in self._poll.poll(timeout):
+                events = 0
+                if event & ~POLLIN:
+                    events |= SELECT_OUT
+                if event & ~POLLOUT:
+                    events |= SELECT_IN
+    
+                key = self._key_from_fd(fd)
+                ready.append((key.fileobj, events, key.data))
+            return ready
+
+
+if 'epoll' in globals():
+
+    class EpollSelector(_BaseSelector):
+        """Epoll-based selector."""
+    
+        def __init__(self):
+            super().__init__()
+            self._epoll = epoll()
+    
+        def register(self, fileobj, events, data=None):
+            key = super().register(fileobj, events, data)
+            epoll_events = 0
+            if events & SELECT_IN:
+                epoll_events |= EPOLLIN
+            if events & SELECT_OUT:
+                epoll_events |= EPOLLOUT
+            self._epoll.register(key.fd, epoll_events)
+    
+        def unregister(self, fileobj):
+            key = super().unregister(fileobj)
+            self._epoll.unregister(key.fd)
+    
+        def select(self, timeout=None):
+            timeout = -1 if timeout is None else timeout
+            max_ev = self.registered_count()
+            ready = []
+            for fd, event in self._epoll.poll(timeout, max_ev):
+                events = 0
+                if event & ~EPOLLIN:
+                    events |= SELECT_OUT
+                if event & ~EPOLLOUT:
+                    events |= SELECT_IN
+    
+                key = self._key_from_fd(fd)
+                ready.append((key.fileobj, events, key.data))
+            return ready
+    
+        def close(self):
+            super().close()
+            self._epoll.close()
+
+
+if 'kqueue' in globals():
+
+    class KqueueSelector(_BaseSelector):
+        """Kqueue-based selector."""
+    
+        def __init__(self):
+            super().__init__()
+            self._kqueue = kqueue()
+    
+        def register(self, fileobj, events, data=None):
+            key = super().register(fileobj, events, data)
+            if events & SELECT_IN:
+                kev = select.kevent(fd, select.KQ_FILTER_READ, select.KQ_EV_ADD)
+                self._kqueue.control([kev], 0, 0)
+            if events & SELECT_OUT:
+                kev = select.kevent(fd, select.KQ_FILTER_WRITE, select.KQ_EV_ADD)
+                self._kqueue.control([kev], 0, 0)
+    
+        def select(self, timeout=None):
+            max_ev = self.registered_count()
+            ready = []
+            for kev in self._kqueue.control(None, max_ev, timeout):
+                fd = kev.ident
+                flag = kev.filter
+                events = 0
+                if flag == select.KQ_FILTER_READ:
+                    events |= SELECT_IN
+                if flag == select.KQ_FILTER_WRITE:
+                    events |= SELECT_OUT
+    
+                key = self._key_from_fd(fd)
+                ready.append((key.fileobj, events, key.data))
+            return ready
+    
+        def close(self):
+            super().close()
+            self._kqueue.close()
+
+
+# Choose the best implementation: roughly, epoll|kqueue > poll > select.
+# select() also can't accept a FD > FD_SETSIZE (usually around 1024)
+if 'KqueueSelector' in globals():
+    Selector = KqueueSelector
+elif 'EpollSelector' in globals():
+    Selector = EpollSelector
+elif 'PollSelector' in globals():
+    Selector = PollSelector
+else:
+    Selector = SelectSelector