From 724354ff470f264a2cb6cd849d444fd99dcbb5f4 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 26 Oct 2015 14:34:54 +0530
Subject: [PATCH] Fix extra close frame being sent during shutdown

---
 src/calibre/srv/web_socket.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/calibre/srv/web_socket.py b/src/calibre/srv/web_socket.py
index ae9e15646e..09451f7791 100644
--- a/src/calibre/srv/web_socket.py
+++ b/src/calibre/srv/web_socket.py
@@ -414,7 +414,7 @@ class WebSocketConnection(HTTPConnection):
                 self.log.exception('Error in WebSocket close handler')
             # Try to write a close frame, just once
             try:
-                if self.send_buf is None:
+                if self.send_buf is None and not self.ws_close_sent:
                     self.websocket_close(SHUTTING_DOWN, 'Shutting down')
                     with self.cf_lock:
                         self.write(self.control_frames.pop())