Check for a closed connection in _add_io_state.

Closes #163.

diff --git a/tornado/iostream.py b/tornado/iostream.py
index 2897fdc77f462f18d2d1850e9846df96467ef24b..4f321d5570050ea561fa482a3c2960ac8c7a4206 100644 (file)
--- a/tornado/iostream.py
+++ b/tornado/iostream.py
@@ -359,6 +359,9 @@ class IOStream(object):
             raise IOError("Stream is closed")
 
     def _add_io_state(self, state):
+        if socket is None:
+            # connection has been closed, so there can be no future events
+            return
         if not self._state & state:
             self._state = self._state | state
             self.io_loop.update_handler(self.socket.fileno(), self._state)